Method of manufacturing multilayer optical information recording medium

ABSTRACT

When a separation layer is formed using a stamper between a substrate and the stamper on a thick substrate, on the surface of which a rewritable recording multilayer film provided with signal guide grooves or pits and the signal guide grooves or pits are transferred from the stamper to the surface, variations in the thickness of the separation layer are produced due to unevenness of the distance between the stamper and the substrate. 
     The surface of the kth signal recording layer of the kth signal substrate is shaped parallel to the surface with the guide grooves and pits of the (k−1)th signal recording layer on the (k−1)th stamper, a (k−1)th separation layer is formed between the two and then the (k−1)th stamper is peeled off. The distance between the surface with the guide grooves and pits of the (k−1)th signal recording layer and the kth signal recording layer becomes uniform, and therefore the thickness of the (k−1)th separation layer can be kept uniform.

This application is a U.S. National Phase Application of PCT ApplicationNo. PCT/JP03/02098, filed Feb. 26, 2003.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a multilayeroptical information recording medium which has n (n: 2 or more) signalrecording layers with a separation layer inserted between the respectivesignal recording layers, one side of which is used to record orreproduce information.

BACKGROUND ART

As a high density optical information recording medium, there is aproposal of a multilayer optical information recording medium having aplurality of signal recording layers in the thickness direction such asa DVD provided with two layers for reproduction on one side. A DVDprovided with two layers for reproduction on one side, for example, hasa structure with two substrates, one having an information recordingsurface on which a translucent reflecting layer of gold or silicon,etc., is formed and the other having an information recording surface onwhich a conventional reflecting layer made of aluminum, etc., is formedand the two substrates are pasted together in such a way that theseinformation recording surfaces come inside facing each other. To furtherimprove surface recording density per one layer, there is a proposal ofa high density optical information recording medium having a violetlaser light source (with a wavelength of approximately 400 nm), a lensof high NA and a 0.1 mm thick low-profile transparent cover layer on therecording/reproducing side. This high density optical informationrecording medium has a structure with signal guide grooves or pitsformed on the surface of a thick signal substrate, a rewritablerecording multilayer film formed thereon and a transparent cover layerfurther formed thereon.

For this low-profile transparent cover layer type high density opticalinformation recording medium, there can also be one with two signalrecording surfaces. One example of the method of manufacturing it willbe shown below.

(1) On a thick substrate on which a rewritable recording multilayer filmwith signal guide grooves or pits formed on the surface is formed, aseparation layer is further formed using UV cure resin and a secondlayer with signal guide grooves or pits is formed on the surface of theseparation layer.

(2) A rewritable translucent recording multilayer film is formed on thesecond layer with signal guide grooves or pits.

(3) A low-profile recording/reproducing side transparent cover layer of0.1 mm in thickness is formed.

An example of specific methods of manufacturing this is the onedescribed in Japanese Patent Laid-Open No. 2002-260307. The entiredisclosure of Japanese Patent Laid-Open No. 2002-260307 is incorporatedherein by reference in its entirety. That is, according to the method ofJapanese Patent Laid-Open No. 2002-260307, using a plastic stamper forthe step in (1) above, UV cure resin is applied to signal guide groovesor pits on the stamper, which are thereby cured, then this is pasted tothe substrate on which the first recording multilayer film is formedusing other UV cure resin having a different nature and the stamper ispeeled off after the cure. Using such a method makes it possible tocreate a multilayer optical information recording medium using a rigidthick substrate as the base and placing one or a plurality of signalrecording layers on top of the base through a separation layer.

However, the separation layer lying between the signal recording layersof the multilayer optical information recording medium must be uniform.When the separation layer is uniform, influences of reflected light fromthe other layer during recording or reproduction become constant in thesignal recording layers before and after the separation layer. When thereflected light from the other signal recording layer fluctuates, thisbecomes a disturbance component of the reproduced signal anddeteriorates S/N. On the contrary, when the separation layer is uniform,disturbance from the other signal recording layer is constant, whichstabilizes recording or reproduction and improves the quality of thereproduced signal. In practice, however, variations in the thickness ofthe separation layer are produced when on a thick substrate on which arewritable recording multilayer film with a surface provided with guidegrooves or pits is formed, a stamper is used to transfer the separationlayer between the substrate and stamper and the signal guide grooves orpits from the stamper onto the surface.

DISCLOSURE OF THE INVENTION

In view of the above described problems, it is an object of the presentinvention to provide a method of manufacturing a multilayer opticalinformation recording medium capable of providing a uniform separationlayer between two signal recording layers.

To solve the above-described problems, a first aspect of the presentinvention is a method of manufacturing a multilayer optical informationrecording medium having n (n is an integer not smaller than 2) signalrecording layers and a separation layer between the respective signalrecording layers, assuming that the kth (k is an integer not smallerthan 2 and not greater than n) signal recording layer from the recordingsurface or reproducing surface is a kth signal recording layer, thesubstrate having said kth signal recording layer on its surface is a kthsignal substrate, the stamper having guide grooves and/or pits of the(k−1)th signal recording layer is a (k−1)th stamper and the separationlayer between the kth signal recording layer and said (k−1)th signalrecording layer is the (k−1)th separation layer, said method ofmanufacturing the multilayer optical information recording mediumcomprising:

a measuring step of measuring surface shapes of one or a plurality ofsaid kth signal substrates manufactured currently or in the past;

a signal recording layer forming step of shaping the surface with guidegrooves and/or pits of said (k−1)th signal recording layer of said(k−1)th stamper so as to correspond to the surface shape of said kthsignal-substrate and forming said (k−1)th signal recording layer usingthe (k−1)th stamper; and

a peeling step of peeling off said (k−1)th stamper from the interfacebetween said (k−1)th separation layer and said (k−1)th stamper,

wherein at least one of said n signal recording layers is created insaid signal recording layer forming step.

According to the above described method of manufacturing the multilayeroptical information recording medium of the present invention, the(k−1)th stamper and the kth signal substrate are shaped parallel to eachother, and therefore the distance between the two becomes uniform andthe thickness of the (k−1)th separation layer created also becomesuniform.

A second aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to thefirst aspect of the present invention, wherein when said kth signalsubstrate is warped so as to wrap around said kth signal recordinglayer, in said signal recording layer forming step, said (k−1)th stamperis warped so as to wrap around the surface opposite to the surface withguide grooves and/or pits of said (k−1)th signal recording layer.

According to the above described configuration, the distance between thekth signal recording layer and the surface having the guide grooves orpits or the guide grooves and pits of the (k−1)th signal recording layerbecomes substantially uniform without changing the warpage of the kthsignal substrate, and therefore the thickness of the manufactured(k−1)th separation layer becomes uniform.

A third aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to thefirst aspect of the present invention, wherein when said kth signalsubstrate is warped so as to wrap around the opposite surface of the kthsignal recording layer, in said signal recording layer forming step,said (k−1)th stamper is warped so as to wrap around the surface withguide grooves and/or pits of said (k−1)th signal recording layer.

According to the above described configuration, the distance between thekth signal recording layer and the surface having the guide grooves orpits or the guide grooves and pits of the (k−1)th signal recording layerbecomes substantially uniform without changing the warpage of the kthsignal substrate, and therefore the thickness of the manufactured(k−1)th separation layer becomes uniform.

A fourth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to thesecond or the third aspect of the present invention, wherein in saidsignal recording layer forming step, the kth signal recording layer ofsaid kth signal substrate and the surface with guide grooves and/or pitsof said (k−1)th signal recording layer are shaped so as to havesubstantially the same radius of curvature.

According to the above described configuration, the distance between thekth signal recording layer and the surface having the guide grooves orpits or the guide grooves and pits of the (k−1)th signal recording layerbecomes substantially uniform without changing the warpage of the kthsignal substrate, and therefore the thickness of the manufactured(k−1)th separation layer becomes uniform.

A fifth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to thefirst aspect of the present invention, wherein said (k−1)th separationlayer is radiation cure resin.

According to the above described configuration, it is possible to easilycure the (k−1)th separation layer formed into a uniform thicknessthrough irradiation with radiation rays and thereby improve theproductivity.

A sixth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to thefifth aspect of the present invention, wherein said radiation cure resinis UV cure resin.

According to the above described configuration, it is possible to use aUV cure type adhesive used for a conventional optical informationrecording medium such as CD and DVD and use their production facilitiesas well.

A seventh aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to thefirst aspect of the present invention, wherein said (k−1)th separationlayer consists of a plurality of layers.

According to the above described configuration, it is possible toarrange materials of different characteristics in the thicknessdirection of the (k−1) th separation layer and stably peel them off, forexample, using a material having good adhesiveness with the kth signalrecording layer as the material contacting the kth signal recordinglayer of the (k−1)th separation layer and using a material which can beeasily peeled away from the (k−1)th stamper as the material contactingthe surface having the guide grooves or pits or the guide grooves andpits of the (k−1)th signal recording layer on the (k−1)th stamper of the(k−1)th separation layer.

An eighth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to theseventh aspect of the present invention, wherein when a layer of saidplurality of (k−1)th separation layers whose guide grooves and/or pitsare transferred from said (k−1)th stamper is used as a transfer layer,of a plurality of interfaces including interfaces of the respectivelayers constituting said (k−1)th separation layer which exists betweensaid (k−1)th stamper and said kth signal recording layer, the interfacebetween said transfer layer and said (k−1)th stamper becomes theinterface which is most easily peeled off.

According to the above described configuration, in the step of peelingoff the (k−1)th stamper from the interface between the (k−1)thseparation layer and the (k−1)th stamper, it is possible to performstable peeling in the interface between the transfer layer and the(k−1)th stamper from among a plurality of interfaces and thereby improveyield in the peeling step.

A ninth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to theseventh aspect of the present invention, wherein when the layer of theplurality of said (k−1)th separation layers whose guide grooves and/orpits are transferred from said (k−1)th stamper is regarded as a transferlayer, at least said transfer layer is a radiation cure material.

According to the above described configuration, the radiation curematerial is easily cured with irradiation with radiation rays, andtherefore it is possible to reliably copy shapes of grooves or pits fromthe (k−1)th stamper.

A tenth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to theninth aspect of the present invention, wherein said radiation curematerial is UV cure resin.

According to the above described configuration, it is also possible touse production facilities used for conventional optical informationrecording medium such as CD and DVD.

An eleventh aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the tenth aspect of the present invention, wherein theviscosity of said UV cure resin is 1 to 1000 mPa·s.

According to the above described configuration, UV cure resin cansufficiently fit into grooves or pits of the (k−1)th stamper, andtherefore it is possible to improve transfers of grooves or pits.

A twelfth aspect of the present invention is the method of manufacturingthe multilayer optical information recording medium according to theseventh aspect of the present invention, wherein when the layer of theplurality of said (k−1)th separation layers whose guide grooves and/orpits are transferred from said (k−1)th stamper is regarded as a transferlayer, at least one of said (k−1)th separation layers other than thetransfer layer is a pressure-sensitive adhesive.

According to the above described configuration, if a pressure-sensitiveadhesive is used as part of the (k−1)th separation layer, it is possibleto form part of the (k−1)th separation layer without performing any,cure process such as radiation cure and thereby improve productivity.

A thirteenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the seventh aspect of the present invention, wherein whenthe layer of the plurality of said (k−1)th separation layers whose guidegrooves and/or pits are transferred from said (k−1)th stamper isregarded as a transfer layer, in said signal recording layer formingstep, a radiation cure material which becomes said transfer layer iscoated on the surface with guide grooves and/or pits of said (k−1)thstamper and cured, and pasted to said kth signal substrate on which said(k−1)th separation layers except said transfer layer are formed.

According to the above described configuration, it is possible to applya radiation cure material which can be easily peeled off after cure tothe (k−1)th stamper as the transfer layer and cure it beforehand andthen transform it into a material which can easily adhere to thetransfer layer which is obtained by curing the material of the side thatcontacts the transfer layer of the (k−1) th separation layer and therebyintegrate the (k−1)th separation layer and reliably peel it off when the(k−1) th stamper is peeled off.

A fourteenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the thirteenth aspect of the present invention, whereinwhen said (k−1)th stamper coated with said transfer layer is pasted tosaid kth signal substrate on which said (k−1)th separation layers exceptsaid transfer layer are formed, the surface of said (k−1)th separationlayer which contacts said transfer layer coated on said (k−1)th stamperis a radiation cure material.

According to the above described configuration, by irradiating radiationrays, it is possible to easily adhere the transfer layer on the (k−1)thstamper to the (k−1)th separation layer on the kth signal substrate.

A fifteenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the seventh aspect of the present invention, wherein whenthe layer of the plurality of said (k−1)th separation layers whose guidegrooves and/or pits are transferred from said (k−1)th stamper isregarded as a transfer layer, in said signal recording layer formingstep, a radiation cure material which becomes said transfer layer isplaced between said (k−1)th stamper and said kth signal substrate onwhich said (k−1)th separation layers except said transfer layer areformed and then said radiation cure material is cured.

According to the above described configuration, if a radiation curematerial is arranged between the (k−1) th stamper and the (k−1)thseparation layer except the transfer layer formed on the kth signalsubstrate, the radiation-cured resin spreads uniformly through acapillary phenomenon and it is possible to further improve uniformity inthe thickness of the separation layer. Furthermore, it is also possibleto easily form a transfer layer through irradiation with radiation rayswhile keeping the uniformity.

A sixteenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the fifteenth aspect of the present invention, wherein insaid signal recording layer forming step, the radiation cure materialwhich becomes said transfer layer is applied to at least one of thesurface on which said (k−1)th separation layers except said transferlayer of said kth signal substrate and the surface with guide groovesand/or pits of said (k−1)th stamper and then said kth signal substrateis superimposed on said (k−1)th stamper and said radiation cure materialis cured.

According to the above described configuration, a radiation curematerial is applied to the entire surface of the (k−1)th stamper or thekth signal substrate before the two are put together, and therefore itis possible to adhere the surface of the (k−1)th stamper to the surfaceof the kth signal substrate and unite the separation layer over theentire surface.

A seventeenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the thirteenth aspect of the present invention, wherein insaid signal recording layer forming step, when said kth signal substrateand said (k−1)th stamper are arranged with said kth signal recordinglayer and the surface with guide grooves and/or pits of said (k−1)thsignal recording layer facing each other, at least one of said kthsignal substrate and said (k−1)th stamper is held in such a way thatsaid (k−1)th stamper is shaped parallel to said kth signal substrate andthen said radiation cure material is cured.

According to the above described configuration, even if the kth signalsubstrate is not shaped parallel to the (k−1)th stamper, the radiationcure material is cured by holding at least one of the two so that theshapes of the two are parallel to each other, and therefore it is notnecessary to control the shapes of the kth signal substrate and the(k−1)th stamper and the margin of creation of the kth signal substrateand the (k−1)th stamper can be widened.

An eighteenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the seventeenth aspect of the present invention, wherein insaid signal recording layer forming step, at least one of said kthsignal substrate and said (k−1)th stamper is fixed onto a support basehaving a desired surface shape and then said radiation cure material iscured.

According to the above described configuration, if the support member isused and the surface shape thereof is kept to a desired shape, it ispossible to easily change the kth signal substrate or the (k−1)thstamper in a shape parallel to each other.

A nineteenth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the first aspect of the present invention, wherein said(k−1)th stamper is made of plastic.

According to the above described configuration, the weight of the(k−1)th stamper is reduced and therefore the (k−1)th stamper can beeasily handled and can also improve productivity.

A twentieth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the nineteenth aspect of the present invention, whereinsaid plastic is transparent.

According to the above described configuration, when the separationlayer is a radiation cure material, it is possible to cure theseparation layer by irradiating radiation rays through the (k−1)thstamper.

A twenty-first aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twentieth aspect of the present invention, wherein said(k−1)th stamper is any one of polycarbonate, olefin resin, acrylic resinor norbornen-based resin and is created according to an injectionmolding method using a metal master stamper.

According to the above described configuration, stampers can be createdat a low cost and in bulk, which improves the capacity of volumeproduction of multilayer optical information recording media.

A twenty-second aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-first aspect of the present invention, whereinin said signal recording layer forming step, when said kth signalsubstrate and said (k−1)th stamper are arranged with the kth signalrecording layer and the surface with guide grooves and/or pits of said(k−1)th signal recording layer facing each other according to theconditions of the injection molding method in creating said (k−1)thstamper, said (k−1)th stamper is controlled so as to be shaped parallelto said kth signal substrate.

According to the above described configuration, the shape of the (k−1)thstamper can be accurately controlled through only injection moldingconditions no matter what kind of warpage the kth signal substrate mayhave.

A twenty-third aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-second aspect of the present invention, whereinin said signal recording layer forming step, when said (k−1)th stamperis created according to the injection molding method in order to shapesaid (k−1)th stamper warped so as to wrap around the surface opposite tothe surface with guide grooves and/or pits of said (k−1)th signalrecording layer, the temperature of the other metal die mirrored surfaceis set higher than the temperature of said metal master stamper placedon one of the pair of molding metal dies.

According to the above described configuration, the surface of the(k−1)th stamper made of plastics formed by an injection molding methodis contracted more because immediately after it is removed from themolding die, the temperature of the surface opposite to the surfaceincluding the guide grooves or pits or the guide grooves and pits ishigher, and it is therefore possible to warp the surface so as to wraparound the surface opposite to the surface including the guide groovesor pits or the guide grooves and pits.

A twenty-fourth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-third aspect of the present invention, whereinin said signal recording layer forming step, the temperature of theother metal die mirrored surface is set higher than the temperature ofthe metal die mirrored surface on which said metal master stamper of thepair of molding metal dies is placed.

According to the above described configuration, the surface of the(k−1)th stamper made of plastics formed by an injection molding methodis contracted more because immediately after it is removed from themolding die, the temperature of the surface opposite to the surfaceincluding the guide grooves or pits or the guide grooves and pits ishigher, and it is therefore possible to warp the surface so as to wraparound the surface opposite to the surface including the guide groovesor pits or the guide grooves and pits.

A twenty-fifth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-third aspect of the present invention, wherein aheat insulator is placed on the back of the metal die mirrored surfaceopposite to the metal die mirrored surface on which said metal masterstamper of the pair of molding metal dies is placed.

According to the above described configuration, for the mirrored surfaceof the metal die opposite to the mirrored surface of the metal die forwhich the metal master stamper is installed, the heat insulator on theback makes it difficult for heat to dissipate, and can therebyeffectively keep the temperature high.

A twenty-sixth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-second aspect of the present invention, whereinin said signal recording layer forming step, when said (k−1)th stamperis created according to the injection molding method in order to shapesaid (k−1)th stamper warped so as to wrap around the surface with guidegrooves and/or pits of said (k−1)th signal recording layer, thetemperature of said metal master stamper placed on the metal diemirrored surface of the pair of molding metal dies is set higher thanthe temperature of the other metal die mirrored surface.

According to the above described configuration, the surface of the(k−1)th stamper made of plastics formed by an injection molding methodis more contracted because immediately after it is removed from themolding die, the temperature of the surface including the guide groovesor pits or the guide grooves and pits is higher than the temperature ofthe opposite surface, and it is therefore possible to warp the surfaceso as to wrap around the surface including the guide grooves or pits orthe guide grooves and pits.

A twenty-seventh aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-sixth aspect of the present invention, whereinin said signal recording layer forming step, the temperature of themetal die mirrored surface on which said metal master stamper of thepair of molding metal dies is placed is set higher than the temperatureof the other metal die mirrored surface.

This makes it easier to make the temperature of the metal master stamperhigher than the temperature of the mirrored surface of the other metaldie.

A twenty-eighth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-sixth aspect of the present invention, wherein aheat insulator is placed on at least one of the back of said metalmaster stamper on which the pair of molding metal dies are placed andthe back of the metal die mirrored surface on which said metal masterstamper is placed.

This method can also inhibit the heat of high-temperature injectedplastics from spreading over the mirrored surface of the metal die andthereby make the temperature of the metal master stamper relativelyhigher than the temperature of the mirrored surface of the other metaldie.

A twenty-ninth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the first aspect of the present invention, wherein said(k−1)th stamper is metal.

According to the above described configuration, since metal has arelatively high degree of hardness, it is possible to suppress damage ordeformation which may occur to the (k−1)th stamper when the (k−1)thstamper is peeled off the kth signal substrate and thereby improve theproductivity of the multilayer optical information recording medium.

A thirtieth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the twenty-ninth aspect of the present invention, whereinin said signal recording layer forming step, when said (k−1)th stamperis created by electrocasting and said kth signal substrate and said(k−1)th stamper are arranged with said kth signal recording layer andthe surface with guide grooves and/or pits of said (k−1)th signalrecording layer facing each other under at least one electrocastingconditions of the pH value, temperature and current density of theelectrocasting bath during electrocasting, said (k−1)th stamper iscontrolled so as to be shaped parallel to said kth signal substrate.

According to the above described configuration, it is possible to createthe (k−1)th stamper easily and at lower cost. Furthermore,electrocasting is a conventional method with an established technology,and can thereby control the shape of the stamper-stably according to theelectrocasting conditions.

A thirty-first aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the first aspect of the present invention, furthercomprising a film forming step after said peeling step, of completingthe (k−1)th signal recording layer by forming a recording multilayerfilm (hereinafter referred to as (k−1)th recording multilayer film) or areflecting film on the guide grooves and/or pits of said transferred(k−1)th signal recording layer.

A thirty-second aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the first aspect of the present invention, wherein a(k−1)th recording multilayer film or a reflecting film is formed on theguide grooves and/or pits of the (k−1)th signal recording layer on said(k−1)th stamper and in said peeling step, said (k−1)th stamper is peeledoff the interface between said (k−1)th recording multilayer film andsaid (k−1)th stamper and said (k−1)th recording multilayer film orreflecting film is moved onto said (k−1)th separation layer.

A thirty-third aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the first aspect of the present invention, wherein atransparent cover layer is formed on the first signal recording layer.

A thirty-fourth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the thirty-third aspect of the present invention, wherein atransparent substrate is adhered to the first signal recording layerwith a transparent adhesive as said transparent cover layer.

According to the above described configuration, it is possible to easilyform a uniform transparent cover layer.

A thirty-fifth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the thirty-third aspect of the present invention, whereinsaid transparent cover layer is formed of a transparent radiation curematerial.

According to the above described configuration, it is possible to reducethe cost.

A thirty-sixth aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the thirty-third aspect of the present invention, whereinat least part of said transparent cover layer is formed of apressure-sensitive adhesive.

According to the above described configuration, it is possible to easilyform a uniform transparent cover layer.

A thirty-seventh aspect of the present invention is the method ofmanufacturing the multilayer optical information recording mediumaccording to the thirty-third aspect of the present invention, whereinthe thickness of the transparent cover layer formed on the first signalrecording layer is about 0.3 mm or less.

According to the above described configuration, when recording orreproduction is performed using a lens with numerical aperture of about0.6 or greater, it is possible to suppress aberration of focused lightcaused by warpage of the multilayer optical information recording mediumand thereby record or reproduce high density information.

Furthermore, the 38th aspect of the present invention is an apparatus ofmanufacturing a multilayer optical information recording mediumcomprising n (n is an integer not smaller than 2) signal recordinglayers and a separation layer between the respective signal recordinglayers, wherein when it is assumed that the kth (k is an integer notsmaller than 2 and not greater than n) signal recording layer from therecording surface or reproducing surface is the kth signal recordinglayer, the substrate having the kth signal recording layer on itssurface is the kth signal substrate, the stamper having guide groovesand/or pits of the (k−1)th signal recording layer is the (k−1)th stamperand the separation layer between the kth signal recording layer and the(k−1)th signal recording layer is the (k−1)th separation layer, theapparatus of manufacturing the multilayer optical information recordingmedium comprises:

measuring means of measuring surface shapes of one or a plurality of thekth signal substrates manufactured currently or in the past;

shape maintaining means of maintaining the surface having the guidegrooves and/or pits of the (k−1)th signal recording layer of the (k−1)thstamper in a shape corresponding to the surface shape of the kth signalsubstrate;

signal recording layer forming means of forming the (k−1)th signalrecording layer using the (k−1)th stamper; and

peeling means of peeling off the (k−1)th stamper from the interfacebetween the (k−1)th separation layer and the (k−1)th stamper.

According to the method of manufacturing the multilayer opticalinformation recording medium of the above described aspect, it is easyto maintain the (k−1)th stamper and the kth signal substrate in a shapeparallel to each other, it is also possible to form a separation layerbetween the two and peel off the (k−1)th stamper and the kth signalsubstrate. In this way, it is possible to manufacture a multilayeroptical information recording medium with the separation layer having auniform thickness.

The 39th aspect of the present invention is the apparatus ofmanufacturing the multilayer optical information recording mediumaccording to the 38th aspect, wherein the shape maintaining meanscomprises a mechanism which holds the (k−1)th stamper so that when thekth signal substrate is warped, the guide grooves and/or pits of the(k−1)th signal recording layer and the kth signal recording layer areparallel to each other according to the warpage of the kth signalsubstrate.

According to the above described configuration, since the guide groovesor pits or the guide grooves and pits of the (k−1)th signal recordinglayer are parallel to the kth signal recording layer according to thewarpage of the kth signal substrate, it is possible to keep uniform thethickness of the (k−1)th separation layer formed between the two.

The 40th aspect of the present invention is the apparatus ofmanufacturing the multilayer optical information recording mediumaccording to the 39th aspect, wherein the shape maintaining means istable-shaped and has the surface shape that contacts the (k−1)th stamperso that the guide grooves and/or pits of the (k−1)th signal recordinglayer are parallel to the kth signal recording layer.

According to the above described configuration, it is possible to easilychange the shape of the (k−1)th stamper with the table-shaped shapemaintaining means.

The 41st aspect of the present invention is the apparatus ofmanufacturing the multilayer optical information recording mediumaccording to the 38th aspect, wherein the shape maintaining meanssupports the surface of at least one of the (k−1)th stamper and the kthsignal substrate for which the (k−1)th separation layer is not formed by“vacuum suction”.

According to the above described configuration, it is possible toreliably maintain the shape of the (k−1)th stamper or the kth signalsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a schematic view showing a step of preparing the kthsignal substrate and the (k−1)th stamper of the method of manufacturinga multilayer optical information recording medium according toEmbodiment 1 of the present invention;

FIG. 1( b) illustrates a step of forming a separation layer between the(k−1)th signal recording layer and the kth signal recording layer of themethod of manufacturing the multilayer optical information recordingmedium according to Embodiment 1 of the present invention;

FIG. 1( c) illustrates a step of performing peeling from an interfacebetween the transferred (k−1)th signal recording layer on the (k−1)thseparation layer and the (k−1)th stamper of the method of manufacturingthe multilayer optical information recording medium according toEmbodiment 1 of the present invention;

FIG. 2( a) illustrates a step of injecting/charging melted polycarbonateinto a molding metal die of the method of creating the (k−1)th stamperin Embodiment 1 of the present invention;

FIG. 2( b) illustrates a step of removing the (k−1)th stamper from themolding metal die of the method of creating the (k−1)th stamper inEmbodiment 1 of the present invention;

FIG. 3( a) illustrates a step of forming transfer layer UV cure resin onthe (k−1)th stamper of the one example of the method of forming the(k−1)th separation layer according to Embodiment 1 of the presentinvention;

FIG. 3( b) illustrates a step of curing the transfer layer UV cure resinby irradiating UV rays of the one example of the method of forming the(k−1)th separation layer according to Embodiment 1 of the presentinvention;

FIG. 3( c) illustrates a step of pasting the (k−1)th stamper on whichthe transfer layer is formed and the kth signal substrate of the oneexample of the method of forming the (k−1)th separation layer accordingto Embodiment 1 of the present invention;

FIG. 3( d) illustrates a step of curing UV cure resin for an adhesive byirradiating UV rays of the one example of the method of forming the(k−1)th separation layer according to Embodiment 1 of the presentinvention;

FIGS. 4( a)-4(b) illustrate examples of a thickness distribution of aseparation layer formed according to the method of manufacturing themultilayer optical information recording medium of the presentinvention;

FIG. 4( a) illustrates an example of a thickness distribution of aseparation layer formed according to the method of manufacturing themultilayer optical information recording medium according to Embodiment1 of the present invention;

FIG. 4( b) illustrates an example of a thickness distribution of aseparation layer formed according to a conventional method;

FIG. 5( a) illustrates a step of forming a transfer layer of the oneexample of the method of manufacturing a conventional multilayer opticalinformation recording medium;

FIG. 5( b) illustrates a step of curing the transfer layer of the oneexample of the method of manufacturing the conventional multilayeroptical information recording medium;

FIG. 5( c) illustrates a step of forming an adhesive layer of the oneexample of the method of manufacturing the conventional multilayeroptical information recording medium;

FIG. 5( d) illustrates a step of completing the (k−1)th separation layerof the one example of the method of manufacturing the conventionalmultilayer optical information recording medium;

FIG. 6( a) illustrates a step of vacuum suctioning of the one example ofthe method of peeling the (k−1)th stamper according to Embodiment 1 ofthe present invention;

FIG. 6( b) illustrates a step of inserting a lug into the interfacebetween the transfer layer and the (k−1)th stamper of the one example ofthe method of peeling the (k−1)th stamper according to Embodiment 1 ofthe present invention;

FIG. 6( c) illustrates a step of pulling up the (k−1)th stamper usinghandling means of the one example of the method of peeling the (k−1)thstamper according to Embodiment 1 of the present invention;

FIG. 6( d) illustrates a step of peeling off the (k−1)th stamper of theone example of the method of peeling the (k−1)th stamper according toEmbodiment 1 of the present invention;

FIG. 7( a) illustrates the method of forming a transparent cover layeraccording to Embodiment 1 of the present invention, which is a method ofarranging an adhesive material between a first signal substrate and afilm and throwing off adhesive material by spinning;

FIG. 7( b) illustrates the method of forming the transparent cover layeraccording to Embodiment 1 of the present invention, which is a method ofadhering of a film using a pressure-sensitive adhesive and forming acover layer;

FIG. 7( c) illustrates the method of forming the transparent cover layeraccording to Embodiment 1 of the present invention, which is a method ofapplying a spin coat to the cover material without using any film;

FIG. 8( a) is a schematic view showing a step of preparing the kthsignal substrate and the (k−1)th stamper of a method of manufacturing amultilayer optical information recording medium according to Embodiment2 of the present invention;

FIG. 8( b) illustrates a step of forming a separation layer between the(k−1)th signal recording layer and the kth signal recording layer of themethod of manufacturing the multilayer optical information recordingmedium according to Embodiment 2 of the present invention;

FIG. 8( c) illustrates a step of performing peeling from the interfacebetween the transferred (k−1)th signal recording layer on the (k−1)thseparation layer and the (k−1)th stamper of the method of manufacturingthe multilayer optical information recording medium according toEmbodiment 2 of the present invention;

FIG. 9( a) illustrates a step of putting the kth signal substrate and apressure-sensitive adhesive into a chamber and vacuuming inside thechamber of the method of forming a separation layer according toEmbodiment 2 of the present invention;

FIG. 9( b) illustrates a step of coating transfer layer UV cure resin tothe surface provided with guide grooves and pits of the (k−1)th signalrecording layer of the method of forming a separation layer according toEmbodiment 2 of the present invention;

FIG. 9( c) illustrates a step of superimposing the (k−1)th stamper onthe kth signal substrate of the method of forming a separation layeraccording to Embodiment 2 of the present invention;

FIG. 9( d) illustrates a step of irradiating UV rays and curing uncuredtransfer layer UV cure resin of the method of forming a separation layeraccording to Embodiment 2 of the present invention;

FIG. 10( a) illustrates a thickness distribution of the separation layerformed using the method of forming a separation layer according toEmbodiment 2 of the present invention;

FIG. 10( b) illustrates a thickness distribution of the separation layerformed using the conventional method of forming a separation layer;

FIG. 11( a) illustrates a step of forming the (k−1)th recordingmultilayer film on the (k−1)th stamper using a target and using asputtering method of the one example of the method of forming therecording multilayer film according to Embodiment 1 of the presentinvention;

FIG. 11( b) illustrates a step of fixing on a peeling table of the oneexample of the method of forming the recording multilayer film accordingto Embodiment 1 of the present invention;

FIG. 11( c) illustrates a step of peeling off the (k−1)th stamper usinghandling means of the one example of the method of forming the recordingmultilayer film according to Embodiment 1 of the present invention;

FIG. 12( a) illustrates a case where a heat insulator is arrangedbetween a master stamper and a metal die mirrored surface A of the oneexample when the (k−1)th stamper is formed using an injection moldingmethod according to Embodiment 3 of the present invention;

FIG. 12( b) illustrates a molding metal die with the heat insulatorincorporated behind the metal die mirrored surface A of the one examplewhen the (k−1)th stamper is formed using the injection molding methodaccording to Embodiment 3 of the present invention;

FIG. 13( a) illustrates a relationship between a cathode current densityand the degree of warpage of the (k−1)th stamper of the conditions whenthe shape of the metal (k−1)th stamper is controlled underelectrocasting conditions according to Embodiment 4 of the presentinvention;

FIG. 13( b) illustrates a relationship between a temperature of anelectrocasting bath and the degree of warpage of the (k−1)th stamper ofthe conditions when the shape of the metal (k−1)th stamper is controlledunder electrocasting conditions according to Embodiment 4 of the presentinvention;

FIG. 13( c) illustrates a relationship between a pH of theelectrocasting bath and the degree of warpage of the (k−1)th stamper ofthe conditions when the shape of the metal (k−1)th stamper is controlledunder electrocasting conditions according to Embodiment 4 of the presentinvention;

FIG. 14( a) illustrates a step of measuring the shape of the kth signalsubstrate according to Embodiment 5 of the present invention;

FIG. 14( b) illustrates a case where the (k−1)th stamper is held by theshape maintaining means according to Embodiment 5 of the presentinvention;

FIG. 14 (c) illustrates a case where UV cure resin for an adhesive layerwhich becomes part of the (k−1)th separation layer is applied in a spacewith the kth signal substrate while the shape of the (k−1)th stamper ismaintained according to Embodiment 5 of the present invention;

FIG. 14( d) illustrates a case where the shape maintaining means holdsthe (k−1)th stamper when the kth signal substrate according toEmbodiment 5 of the present invention is warped in such a way as to wraparound the surface opposite to the surface with the kth signal recordinglayer;

FIG. 15( a) illustrates a step of measuring the shape of the kth signalsubstrate, which is a second example of the shape maintaining means andthe separation layer forming means according to Embodiment 5 of thepresent invention;

FIG. 15( b) illustrates a step of maintaining the shape of the (k−1)thstamper, which is the second example of the shape maintaining means andthe separation layer forming means according to Embodiment 5 of thepresent invention;

FIG. 15( c) illustrates a step of applying adhesive layer UV cure resinwhich becomes part of the separation layer, which is the second exampleof the shape maintaining means and the separation layer forming meansaccording to Embodiment 5 of the present invention; and

FIG. 15( d) illustrates a step of holding the (k−1)th stamper using aconcave shape maintaining table, which is the second example of theshape maintaining means and the separation layer forming means accordingto Embodiment 5 of the present invention.

DESCRIPTION OF SYMBOLS

-   103, 306, 803, 900 kth signal substrate-   100, 800 kth signal recording layer-   101, 801 (k+1)th signal recording layer-   102, 802 nth signal recording layer-   110 kth separation layer-   105, 805 guide grooves and pits of (k−1)th signal recording layer-   106, 204, 300, 500, 806, 902 (k−1)th stamper-   107, 310, 510, 807, 909 (k−1)th separation layer-   108, 808 guide grooves and pits of transferred (k−1)th signal    recording layer-   200 molding metal die-   201 master stamper-   202 polycarbonate-   203 cavity-   205 surface on which guide grooves and pits are formed-   206 surface on opposite side-   305, 309, 509, 720, 904 table-   301, 903 transfer layer UV cure resin-   302, 910 UV lamp-   303, 503 transfer layer-   307 adhesive layer UV cure resin-   308, 508, 730 adhesive layer-   600 peeling table-   610 lug-   615 air-   612 handling means-   700 film-   710 first signal substrate-   740, 901 pressure-sensitive adhesive-   745, 905 chamber-   750 cover material-   1100 target-   1101 (k−1)th recording multilayer film-   1200 heat insulator-   1400 shape maintaining arm-   1401 warpage measuring means-   1402 measuring light-   1403 nozzle-   1500 shape maintaining table-   1501 concave shape maintaining table-   D1 diameter of central hole of pressure-sensitive adhesive-   D0 diameter of central hole of kth signal substrate and central hole    of (k−1)th stamper-   D2 inside diameter of transfer layer UV cure resin

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, embodiments of the presentinvention will be explained in detail below.

Embodiment 1

FIGS. 1( a)-1(c) show an embodiment of a method of manufacturing amultilayer optical information recording medium according to the presentinvention. FIGS. 1( a)-1(c) are schematic views of a step of forming a(k−1)th separation layer 107 between a kth signal recording layer 100and a (k−1)th signal recording layer of a disk type multilayer opticalinformation recording medium having n (n: 2 or more) signal recordinglayers and a separation layer between the respective signal recordinglayers recording and reproducing information to/from one side. Here,suppose the kth signal recording layer 100 is the kth (k: 2 or above andn or below) signal recording layer from the recording/reproductionsurface and a substrate having the kth signal recording layer 100 on thesurface is a kth signal substrate 103. Furthermore, suppose the stamperhaving guide grooves and pits 105 of the (k−1)th signal recording layeris a (k−1)th stamper 106.

The step of forming a (k−1)th separation layer 107 of this embodiment isan example of the step of forming a signal recording layer of thepresent invention.

The method of manufacturing the multilayer optical information recordingmedium of Embodiment 1 is intended to manufacture a high density opticalinformation recording medium having a low-profile recording/reproducingside transparent cover layer of about 0.3 mm or less and about 2 micronsor above in thickness using a violet laser light source (wavelength ofapproximately 400 nm) and a high NA lens to improve the surfacerecording density per one layer. The methods of manufacturing multilayeroptical information recording media of embodiments other than Embodiment1 are also intended to manufacture a high density optical informationrecording medium similar to that of Embodiment 1. It goes without sayingthat it is possible to apply the method of manufacturing the multilayeroptical information recording medium of this embodiment to any mediaother than such a high density optical information recording medium.

Both the kth signal substrate 103 and the (k−1)th stamper 106 in FIGS.1( a)-1(c) are disk-shaped and have a central hole in the center. Thekth signal substrate 103 is designed to have a warped shape makingallowances for warpage that can occur in other steps following the stepof forming the (k−1)th separation layer 107 such as the step of forminga signal recording layer or a step of forming a transparent cover layeron the first signal recording layer. Furthermore, the kth signalsubstrate 103 is generally naturally warped due to stress caused in thestep of forming the kth recording multilayer film of the kth signalrecording layer 100, the step of forming the (k−1)th to nth separationlayers and the step of forming the (k−1)th to nth recording multilayerfilms, etc. This Embodiment 1 shows the kth signal substrate 103 warpedso as to wrap around the kth signal recording layer 100 as an example.

First, the kth signal substrate 103 is prepared as shown in FIG. 1( a).In addition to the kth signal recording layer 100 on its surface, thekth signal substrate 103 has a total of (n-k−1) signal recording layersfrom the (k−1)th signal recording layer 101 up to the nth signalrecording layer 102. Here, the signal recording layer consists of guidegrooves for guiding recording light and reproducing light to record datain and reproduce data from the multilayer optical information recordingmedium, pits indicating address information, phase variation films suchas GeSbTe and AgInSbTe, recording films represented by magnetic filmsand pigment films and recording multilayer film made of a dielectricfilm such as ZnS sandwiching them or reflecting film. Furthermore, aseparation layer represented by the kth separation layer 110 is arrangedbetween the respective signal recording layers. The multilayer opticalinformation recording medium of this embodiment is not limited to theone made up of only guide grooves in which video/audio data is writtenafter manufacturing but can also be the one made up of pits in whichvideo/audio data is written during manufacturing or the one with pitsformed inside or outside the guide grooves.

On the other hand, the (k−1)th stamper 106 having guide grooves and pits105 of the (k−1)th signal recording layer on its surface is alsoprepared. The (k−1)th stamper 106 has been created by measuring thesurface shape of one or a plurality of the kth signal substrates 103which have been created currently or in the past as in the case ofwarpage measuring means 1401 which will be shown in FIG. 14 ofEmbodiment 5 which will be described later and based on the measurementresult, transforming the surface having guide grooves and pits 105 ofthe (k−1) th signal recording layer of the (k−1)th stamper 106 into theshape corresponding to the surface shape of the kth signal substrate103. That is, the (k−1)th stamper 106 has been formed so as to conformto the shape of the kth signal substrate 103.

Then, the surface shape of the kth signal substrate 103 may be measuredby measuring the surface shape of the kth-signal substrate 103manufactured first in the morning the day before when the plant operatesand determining the shape of the (k−1)th stamper 106 based on themeasurement result. Furthermore, it is also possible to measure theshape of the kth signal substrates 103 one by one every time the kthsignal substrate 103 is manufactured and determine the shape of the(k−1)th stamper 106 based on the measurement result. Furthermore, it isalso possible to determine the shape of the (k−1)th stamper 106 usingthe measurement result of the shape surface of the kth signal substrate103 for each lot.

That is, by measuring the shape of the kth signal substrate 103 anddetermining the shape of the (k−1)th stamper 106 from the measurementresult, the (k−1)th stamper 106 and the kth signal substrate 103 come tohave shapes parallel to each other as shown in the figure. That is, theguide grooves and pits 105 of the (k−1)th signal recording layer and thekth signal recording layer 100 are arranged parallel to each other andthe distance between the two becomes uniform in the radial direction andwithin the surface. That is, the kth signal recording layer 100 of thekth signal substrate 103 and the surface having guide grooves and/orpits 105 of the (k−1)th signal recording layer are shaped so as to havesubstantially the same curvature radius. In general, a substrate havinga plurality of signal recording layers as in the case of the kth signalsubstrate 103 is warped due to stress of the films such as recordingmultilayer films and reflecting films. Thus, the (k−1)th stamper 106 ofthis embodiment is shaped so as to be parallel to the already warped kthsignal substrate 103 and guide grooves and pits 105 of the (k−1)thsignal recording layer and the kth signal recording layer 100 arearranged so as to face each other.

Then, as shown in FIG. 1( b), the (k−1)th separation layer 107 is formedbetween the guide grooves and pits 105 of the (k−1)th signal recordinglayer and the kth signal recording layer 100. At this time, it isnecessary to ensure that the (k−1)th stamper side of the (k−1)thseparation layer 107 fit into the guide grooves and pits 105 of the(k−1)th signal recording layer. In FIG. 1(1), the distance between theguide grooves and pits 105 of the (k−1)th signal recording layer and thekth signal recording layer 100 is uniform in the radial direction andwithin the surface, and therefore the thickness of the (k−1)thseparation layer 107 becomes uniform. The (k−1)th separation layer 107need not always be made of one material but may also be made up of aplurality of layers made of different materials. For example, when thelayer contacting the guide grooves and pits 105 of the (k−1)th signalrecording layer of the (k−1)th separation layer 107 is used as atransfer layer, if a liquid material having a curing characteristic isused as a transfer layer, it is easily fitted into the guide grooves andpits 105 of the (k−1)th signal recording layer and it is possible toimprove transferability. In this case, the transfer layer is cured andthe (k−1)th separation layer 107 is completed.

Then, as shown in FIG. 1( c), peeling is performed from the interfacebetween the guide grooves and pits 108 of the transferred (k−1)th signalrecording layer on the (k−1)th separation layer 107 and the (k−1)thstamper 106. Such peeling can provide the (k−1)th signal substrate. Toensure the peeling, it is important that the interface between the(k−1)th separation layer 107 and the (k−1)th stamper 106 be the one thatcan be peeled most easily from among a plurality of interfaces thatexist between the (k−1)th stamper 106 and the kth signal recording layer100. To this effect, it is possible to select the material of thetransfer layer, material of the (k−1)th stamper 106 and material of itssurface, etc.

As shown above, it is possible to form a uniform separation layer byshaping the guide grooves and pits 105 of the (k−1)th signal recordinglayer of the (k−1)th stamper 106 and the kth signal recording layer 100on the kth signal substrate 103 parallel to each other and forming the(k−1)th separation layer 107. Manufacturing all of the plurality ofseparation layers in the above described steps makes it possible toimprove the accuracy of the overall multilayer optical informationrecording medium and drastically improve the information recording orreproducing performance of each signal recording layer.

Examples of the respective steps in above described FIGS. 1( a)-1(c)will be explained in detail below. FIGS. 2( a)-2(b) show steps offorming the (k−1)th stamper. Here, plastic is used as the material ofthe (k−1)th stamper. Plastic is light, has an excellent operability andis convenient because it can be easily created in bulk using aninjection molding method. It also has an advantage that a desired shape(warpage) can be provided by controlling molding conditions. Here,polycarbonate is used as the material of the (k−1)th stamper. Inaddition to polycarbonate, olefin resin, acrylic resin andnorbornen-based resin, etc., can also be used.

First, as shown in FIG. 2( a), a master stamper 201 is placed on a metaldie mirrored surface A of a pair of molding metal dies 200 andpolycarbonate 202 melted at about 380° C. is molded and charged into themolding metal die 200. The master stamper 201 is made of, for example, amaterial whose principal ingredient is metal such as nickel. A cavity203 formed between the master stamper 201 of the molding metal die 200and the metal die mirrored surface B is predetermined to have a desiredthickness of the (k−1)th stamper. Here, the thickness of the cavity 293for forming the (k−1)th stamper of approximately 1.1 mm in thickness is1.1 mm. The metal die mirrored surface A and the metal die mirroredsurface B of the molding metal die 200 are set to their respectivetemperatures.

Here, the temperatures of the metal die mirrored surfaces A and B areset to about 115° C. and about 125° C. respectively so that(temperatures of metal die mirrored surface A)<(temperatures of metaldie mirrored surface B). These temperatures allow the polycarbonate 202melted at 380° C. to be cooled and calcified. When polycarbonate isinjected/charged, a mold pressing force of about 20 to 30 t is appliedto the molding metal die 200. The mold pressing force causes the meltedpolycarbonate to fit into the guide grooves and pits formed in themaster stamper 201 and to transfer them.

After cooling (e.g., for 10 seconds), as shown in FIG. 2( b), the(k−1)th stamper 204 is removed from the molding metal die 200. At thistime, since (temperature of metal die mirrored surface A)<(temperatureof metal die mirrored surface B), the temperature of the surface 205 onwhich guide grooves and pits of the (k−1)th stamper 204 are formed islower than the temperature of the surface 206 on the opposite side.Therefore, the amount of contraction when the temperature is lowered toa room temperature is greater on the surface 206 on the opposite sideand as a result, the (k−1)th stamper 204 acquires a shape wrappingaround the surface 206 on the opposite side. The (k−1)th stamper 106shown in FIG. 1(1) is created in this way.

FIGS. 3( a)-3(d) show steps of forming the (k−1)th separation layer.According to Embodiment 1, the (k−1)th separation layer is made of twomaterials and a case where both the outside diameter of the kth signalsubstrate and the outside diameter of the (k−1)th stamper are 120 mmwill be explained using an example. First, as shown in FIG. 3( a), a(k−1)th stamper 300 is placed on a table 305 with the surface providedwith guide grooves and pits of the (k−1)th stamper facing upward. The(k−1)th stamper 300 can be created using the method shown in FIGS. 2(a)-2(b). The (k−1)th stamper 300 set is fixed onto the table 305 using amethod such as vacuum suction. At this time, the surface shape of thetable 305 is preferably shaped with the same curvature as that of the(k−1)th stamper as shown in the figure. This is because the shape of the(k−1)th stamper 300 itself is controlled in the steps shown in FIGS. 2(a)-2(b).

With transfer layer UV cure resin 301 dribbled onto the surface with theguide grooves and pits of the (k−1)th stamper, the table 305 is turnedto throw off extra transfer layer UV cure resin and a layer of thetransfer layer UV cure resin of a uniform thickness is obtained. As theUV cure resin, acrylic resin which radically reacts with irradiation ofUV rays is preferable. In this embodiment, acrylic UV cure resin with aviscosity of 200 MPa·s which can be easily peeled from the polycarbonate(k−1)th stamper 300 is used. UV cure resin with a viscosity of about 1to 1000 MPa·s can well fit into the projections and depressions of guidegrooves and pits on the stamper. Through spinning at a speed of 4000 rpmfor 5 seconds, a transfer layer of approximately 8 microns in thicknesswas obtained.

Then, as shown in FIG. 3( b), UV rays are irradiated using a UV lamp302. As the UV lamp 302, a metal halide lamp, high pressure mercury lampor xenon lamp, etc., is preferably used. Irradiation with UV rays curesthe transfer layer UV cure resin 301 and forms a transfer layer 303.

Then, as shown in FIG. 3( c), the (k−1)th stamper 300 on which thetransfer layer 303 is formed is pasted to the kth signal substrate 306.In the kth signal substrate 306, not only the guide grooves and pits ofthe kth signal recording layer and kth recording multilayer film areformed, but also the (k+1)th to nth signal recording layers (not shown)are included. With the kth signal substrate 306 fixed on a table 309 bymeans of vacuum suction, an adhesive layer UV cure resin 307 whichbecomes an adhesive is dribbled onto the kth signal recording layer andthe transfer layer 303 of the (k−1) th stamper 300 is placed so as tocontact the adhesive layer UV cure resin 307. Then, the table 309 isturned as shown in the figure to throw off extra adhesive layer UV cureresin. In this embodiment, the table was turned at 5000 rpm for 8seconds. As the adhesive layer UV cure resin 307, acrylic UV cure resinof 600 mpa·s with high strength of adhesion to the kth recordingmultilayer film and transfer layer 303 was used.

Then, as shown in FIG. 3( d), UV rays are irradiated from the UV lamp302 to cure the adhesive layer UV cure resin 307. As the UV lamp 302, ametal halide lamp, high pressure mercury lamp or xenon lamp, etc., canbe used as in the case of above described FIG. 3( b). The (k−1)thstamper 300 has transparency such as polycarbonate, and therefore canallow UV rays to penetrate to some extent to cure the adhesive layer UVcure resin 307. After the cure, the average thickness of the adhesivelayer 308 is 22 microns and the transfer layer 303 and adhesive layer308 which have been united by the cure becomes a (k−1)th separationlayer 310.

The thickness of the (k−1)th separation layer 310 was as shown in FIG.4( a). In FIG. 4( a), the thickness of the (k−1)th separation layer inthe radial direction was 27 to 31 microns, which is a variation of 4microns, which can be considered uniform. On the other hand, FIG. 4( b)shows a thickness variation of the (k−1)th stamper in the radialdirection of the (k−1)th separation layer created using a conventionalmethod. The thickness tends to increase toward the inside radius and hasa large variation of 14 microns in the range of 23 to 37 microns. Inthis embodiment, as shown in FIG. 4( a), the thickness variation of the(k−1)th separation layer in the radial direction is about 4 microns,which can be considered uniform, but it is possible to maintain theperformance of a high density optical information recording medium ifthe variation is within about 6 microns.

FIGS 5(a)-5(d) show how the (k−1)th separation layer is created when the(k−1)th stamper is created into a flat shape using the injection moldingmethod as in the conventional method. It is substantially the same asthe steps shown in FIG. 3 except that the shape of the (k−1)th stamper500 is flat. FIGS. 5( a) and 5(b) show the step of forming a transferlayer 503, while FIGS. 5( c) and 5(d) show the step of forming anadhesive layer 508 and completing a (k−1)th separation layer 510. Sincethe shape of the (k−1)th stamper 500 is flat, it is natural that a table505 be flat. Furthermore, since the (k−1)th stamper 500 is flat as shownin FIG. 5( c), the distance between the surface with guide grooves andpits of the (k−1)th stamper 500 and the kth signal recording layer ofthe kth signal substrate 306 increases toward the inside radius. Forthis reason, the thickness of an adhesive layer 508 increases toward theinside radius as shown in FIG. 5( d) and as a result, the thickness ofthe (k−1)th separation layer 510 consisting of the adhesive layer 508and transfer layer 503 also increases toward the inside radius.

FIGS. 3( a)-3(d) describe the steps of forming the (k−1)th separationlayer, but steps shown in (A) to (C) below are also effective instead.

(A) In the step in FIG. 3( a), transfer layer UV cure resin is appliedto the (k−1)th stamper but it is not cured with UV rays. On the otherhand, using the same method as that in FIG. 3( a), adhesive layer UVcure resin is applied to the kth signal substrate. After the (k−1)thstamper is superimposed on the kth signal substrate in a chamber under areduced pressure, the transfer layer UV cure resin and adhesive layer UVcure resin are cured with UV rays as shown in FIG. 3( d).

(B) In the step in FIG. 3( a), transfer layer UV cure resin is appliedto the (k−1)th stamper and this is cured with UV rays as shown in FIG.3( b). On the other hand, using the same method as that in FIG. 3( a),adhesive layer UV cure resin is applied to the kth signal substrate.After the (k−1)th stamper is superimposed on the kth signal substrate ina chamber under a reduced pressure, the adhesive layer UV cure resin iscured with UV rays as shown in FIG. 3( d).

(C) In the step in FIG. 3( a), transfer layer UV cure resin is appliedto the (k−1)th stamper and this is not cured with UV rays. On the otherhand, using the same method as that in FIG. 3( a), adhesive layer UVcure resin is applied to the kth signal substrate and cured with UVrays. After the (k−1)th stamper is superimposed on the kth signalsubstrate in a chamber under a reduced pressure, the transfer layer UVcure resin is cured with UV rays as shown in FIG. 3( d).

Furthermore, FIG. 3( c) has described the case where with the kth signalsubstrate 306 fixed on the table 309 by means of vacuum suction, theadhesive layer UV cure resin 307 which becomes an adhesive is dribbledonto the kth signal recording layer and the transfer layer 303 of the(k−1)th stamper 300 is placed from above so as to contact the adhesivelayer UV cure resin 307, then the table 309 is turned to throw off extraadhesive layer UV cure resin, but the method is not limited to this.

It is also possible to form a layer of transfer layer UV cure resin 301on the (k−1)th stamper 300, apply the adhesive layer UV cure resin 307onto the (k−1)th stamper 300 on which the layer of the transfer layer UVcure resin 301 is formed and then paste the (k−1)th stamper 300 to thekth signal substrate 306. It is further possible to apply the adhesivelayer UV cure resin 307 onto the kth signal substrate 306, apply thetransfer layer UV cure resin 301 onto the adhesive layer UV cure resin307 of the kth signal substrate 306 and then paste the (k−1)th stamper300 to the kth signal substrate 306.

FIGS. 6( a)-6(d) steps. The (k−1)th stamper 300 and the kth signalsubstrate 306 bonded together in the step shown in FIGS. 3( a)-3(d) arefixed on a peeling table 600. The means of fixing can be vacuum suctionin FIG. 6( a), but other means include, for example, a machine whichholds the circumferential end surface of the kth signal substrate 306.Then, as shown in FIG. 6( b), a lug 610 is inserted into the centralhole of the (k−1)th stamper 300 and the kth signal substrate 306 and thelug 610 is inserted into the interface between the transfer layer 303which is part of the (k−1)th separation layer 310 and the (k−1)thstamper 300. As the end of the lug 610 is sharp, the lug 610 can beeasily inserted as a wedge into the interface between the transfer layer303 and the (k−1)th stamper 300.

As shown in FIG. 6( c), while the lug 610 is being opened outward,pressurized air 615 is introduced from the center of the peeling table600 into the area between the transfer layer 303 and the (k−1)th stamper300. At this time, the (k−1)th stamper 300 is pulled up using thehandling means 612. Pulling it up using the handling means 612facilitates the peeling. Finally, the (k−1)th stamper 300 is peeled offas shown in FIG. 6( d).

The (k−1)th recording multilayer film is formed on the guide grooves andpits of the (k−1)th signal recording layer transferred on the (k−1)thseparation layer. Though the method of forming the (k−1)th recordingmultilayer film varies depending on the material, phase variation filmssuch as GeSbTe and AgInSbTe, recording films such as magnetic films,dielectric films such as ZnS sandwiching them and metal reflecting film,etc., are formed by sputtering and vapor deposition. Furthermore, in thecase of the pigment film, spin coating is used. It is only after the(k−1)th recording multilayer film is formed that the (k−1)th signalrecording layer is completed. By repeating the steps shown in FIGS. 2(a)-2(b). FIGS. 3( a)-3(d) and FIGS. 6( a)-6(d) and formation of therecording multilayer film on the (k−1)th signal recording layer, a firstsignal substrate having n signal recording layers is created.

In addition to the above described film forming method, a method shownin FIGS. 11( a)-11(c) can also be used. This is effective when it isdifficult to form the (k−1)th recording multilayer film on the guidegrooves and pits of the (k−1)th signal recording layer transferred ontothe (k−1)th separation layer. As shown in FIG. 11( a), the (k−1)threcording multilayer film 1101 is formed on the (k−1)th stamper 300beforehand using a target 1100 and using a sputtering method. Here, onlyone target is shown, but since the (k−1)th recording multilayer film1101 is actually made of a plurality of materials, a plurality oftargets are necessary. Then, in the steps in FIGS. 3( a)-3(d), the(k−1)th separation layer 310 consisting of the transfer layer 303 andadhesive layer 308 is formed.

Then, as shown in FIG. 11( b), the (k−1)th separation layer 310 is fixedon the peeling table 600 and as shown in FIG. 11( c), the (k−1)thstamper 300 is peeled using the handling means 612. The procedure up tothe peeling is the same as that shown in FIG. 6, and therefore it isomitted here. At this time, the (k−1)th stamper 300 is peeled off the(k−1)th recording multilayer film 1101 and the (k−1)th recordingmultilayer film 1101 is moved onto the (k−1)th separation layer 310.Guide grooves and pits are formed on the transfer layer 303 and at thesame time the (k−1)th recording multilayer film 1101 is also formed.Using this step makes it possible to form the (k−1)th separation layeronto the kth signal substrate and at the same time form the (k−1)threcording multilayer film and there is an expectation of shortening of atact time.

FIGS. 7( a)-7(c) show examples of steps of creating a transparent coverlayer on the first signal recording layer. In the case shown here, thethickness of the transparent cover layer is 100 microns. In FIG. 7( a),a film 700 of 90 microns in thickness is bonded on the table 720 usingan adhesive layer 730 of 10 microns in thickness by spin coating to formthe cover layer. As the material of the film 700, polycarbonate, olefinresin or norbornen-based resin, etc., can be used. As the adhesive layer730, UV cure resin, radiation-cured material such as heat-cured resincan be used.

As the bonding procedure, as shown in FIG. 7( a) a method of arrangingan adhesive material between a first signal substrate 710 and film 700and throwing it off by spinning, a method of superimposing the firstsignal substrate 710 on the film 700 and spinning or a method ofapplying an adhesive material to the entire surface of at least one ofthe first signal substrate 710 and film 700 beforehand and pasting themtogether in vacuum, etc., is available. In any method, after the firstsignal substrate 710 and the film 700 are overlapped through theadhesive material, they need to be cured.

FIG. 7( b) shows a method of bonding the film 700 using apressure-sensitive adhesive 740 and forming a cover layer. In this case,the thickness of the pressure-sensitive adhesive 740 is 20 to 30 micronsand the thickness of the film 700 obtained by subtracting the thicknessof the pressure-sensitive adhesive 740 from 100 microns is used. Thebonding method used is, for example, a method of overlapping the film700 with the pressure-sensitive adhesive 740 in the chamber 745 with areduced pressure shown in FIG. 7( b). After overlapping them, the filmsurface is pressed with a high-pressure compressed air to secure thebonding. In addition to this method, a method of pasting using a rollerin the atmosphere or under a reduced pressure may also be used.

FIG. 7( c) shows a method whereby a cover material 750 is applied byspin coating without using any film. Optimizing the condition ofsupplying the cover material 750 and the condition of spin rotationmakes it possible to form a uniform transparent cover layer of 100microns in thickness. Using the above described methods shown in FIGS.7( a)-7(c), the transparent cover layer is formed and a multilayeroptical information recording medium is completed.

In above described Embodiment 1, the plastic (k−1)th stamper of 1.1 mmin thickness is used, but any plastic stamper that has a thickness of atleast 0.5 mm is acceptable. If the stamper has a thickness of about 0.5mm or more, since it also has rigidity, its shape can be easilycontrolled according to the molding condition using the injectionmolding method and it can be easily handled, which is suited toimproving productivity.

Furthermore, Embodiment 1 has described the case where the (k−1)thseparation layer is made of two materials, but it is also applicable toa case where the (k−1)th separation layer is made of three or morematerials. Furthermore, Embodiment 1 has been described using UV cureresin, but it is also possible to use a radiation cure materialincluding a heat cure material.

Embodiment 2

Embodiment 2 of the method of manufacturing a multilayer opticalinformation recording medium according to the present invention will beexplained. FIGS. 9( a)-8(c) show a case with warpage opposite to that inEmbodiment 1, that is, a case where the kth signal substrate is warpedso as to wrap around the surface opposite to the kth signal recordinglayer. As with FIGS. 1( a)-1(c), both the kth signal substrate and the(k−1)th stamper in FIGS. 8( a)-8(c) have a disk shape and have a centralhole in the center.

First, as shown in FIG. 8( a), the kth signal substrate 803 is providedwith not only the kth signal recording layer 800 on the surface of thekth separation layer 810 but also a total of (n-k−1) signal recordinglayers from the (k−1)th signal recording layer 801 to the nth signalrecording layer 802. As in the case of Embodiment 1, the signalrecording layer consists of guide grooves for guiding recording light orreproducing light when information is recorded in or reproduced from themultilayer optical information recording medium or pits indicatingaddress information, phase variation film such as GeSbTe or AgInSbTe,recording film represented by magnetic film and pigment film andrecording multilayer film made of dielectric films such as ZnSsandwiching them or reflecting film.

On the other hand, the (k−1)th stamper 806 having the guide grooves andpits 805 of the (k−1)th signal recording layer on the surface is alsoprepared. The (k−1)th stamper 806 is formed by measuring the surfaceshapes of one or a plurality of kth signal substrates 803 manufacturedcurrently or in the past as in the case of warpage measuring means 1401which will be shown in FIGS. 14( a)-14(d) of Embodiment 5 as will bedescribed later, shaping the surface with guide grooves and/or pits 805of the (k−1)th signal recording layer of the (k−1)th stamper 806 toconform to the surface shape of the kth signal substrate 803 based onthe measurement result. That is, the (k−1)th stamper 806 is in a shapeparallel to the kth signal substrate 803.

Therefore, the (k−1)th stamper 806 and the kth signal substrate 803 areshaped parallel to each other as shown in the figure and the (k−1)thstamper 806 is warped so as to wrap around the guide grooves and pits805 of the (k−1)th signal recording layer. That is, the guide groovesand pits 805 of the (k−1)th signal recording layer and the kth signalrecording layer 800 are shaped parallel to each other and the distanceis uniform in the radial direction and within the surface. That is, thekth signal recording layer 800 of the kth signal substrate 803 and thesurface with the guide grooves and/or pits 805 of the (k−1)th signalrecording layer are shaped so as to have substantially the same radiusof curvature.

Then, as shown in FIG. 8( b), a (k−1)th separation layer 807 is formedbetween the guide grooves and pits 805 of the (k−1)th signal recordinglayer and the kth signal recording layer 800. At this time, the (k−1)thstamper side of the (k−1)th separation layer 807 needs to be formed soas to fit into the guide grooves and pits 805 of the (k−1)th signalrecording layer. In FIG. 8( a), since the distance between the guidegrooves and pits 805 of the (k−1)th signal recording layer and the kthsignal recording layer 800 is uniform in the radial direction and withinthe surface, the thickness of the (k−1)th separation layer is uniform.The (k−1)th separation layer 807 need not only be made of one materialbut also may be made up of a plurality of layers made of differentmaterials. For example, when the layer of the (k−1)th separation layer807 which contacts the guide grooves and pits 805 of the (k−1)th signalrecording layer is regarded as a transfer layer, if a liquid materialwith a curing characteristic is used as the transfer layer, it is easilyfitted into the guide grooves and pits 805 of the (k−1)th signalrecording layer and transferability can be improved. In this case, thetransfer layer is cured and the (k−1)th separation layer 807 iscompleted.

Then, as shown in FIG. 8( c), peeling is performed from the interfacebetween the guide grooves and pits 808 of the transferred (k−1)th signalrecording layer on the (k−1)th separation layer 807 and the (k−1)thstamper 806.

As shown above, even if the warpage of the kth signal substrate isdifferent from that of Embodiment 1, providing the (k−1)th stamper withreverse warpage makes the distance between the kth signal substrate andthe (k−1)th stamper uniform in the radial direction, so as to keep thethickness of the (k−1)th separation layer uniform. For example, if the(k−1)th stamper is made of plastic as in the case of Embodiment 1, the(k−1)th stamper can be created using the injection molding method shownin FIGS. 2( a)-2(b). By setting the temperature of the metal diemirrored surface A in FIGS. 2( a)-2(b) to a temperature higher than thatof the metal die mirrored surface B, the (k−1)th stamper 204 is shapedso as to wrap around the surface 205 on which the guide grooves and pitsare formed after it is removed from the molding metal die 200.

Then, a specific example of the method of forming the (k−1)th separationlayer shown in FIG. 8( b) will be explained. FIGS. 9( a)-9(d) showexamples of forming the (k−1)th separation layer of 30 microns inthickness using a pressure-sensitive adhesive and a transfer layer.FIGS. 9( a)-9(d) show a method of using a pressure-sensitive adhesive aspart of the (k−1)th separation layer. The pressure-sensitive adhesivehas excellent thickness accuracy because it has a semi-solid film-likeshape. On the other hand, having a very high viscosity, it is difficultfor the pressure-sensitive adhesive to transfer the guide grooves andpits of the (k−1)th stamper. This formation method uses a transfer layerwith a low viscosity separately.

First, as shown in FIG. 9( a), a kth signal substrate 900 and apressure-sensitive adhesive 901 of 25 microns in thickness are put in achamber 905 and the chamber 905 is vacuum-sealed. As the degree ofvacuum, for example, a range of about 1 to 100 hPa is appropriate. Then,the pressure-sensitive adhesive 901 is superimposed on the surface ofthe kth signal recording layer of the kth signal substrate 900. At thistime, it is preferable to superimpose the pressure-sensitive adhesive901 gradually starting from the central area outward. By doing so, it ispossible to suppress the increase of stress in the kth signal substrate900 caused by the superimposition of the pressure-sensitive adhesive901. Furthermore, the pressure-sensitive adhesive 901 has a central holehaving a diameter of D1. D1 is greater than the diameter of the centralhole D0 of the kth signal substrate. After the superimposition, the kthsignal substrate and the pressure-sensitive adhesive are taken out intothe atmosphere and the pressure-sensitive adhesive may be pressed undera high-pressure compressed air to secure the adhesion.

Simultaneously with FIG. 9( a), the (k−1)th stamper 902 is fixed onto atable 904 as shown in FIG. 9( b), a transfer layer UV cure resin 903 iscoated over the surface with guide grooves and pits of the (k−1)thsignal recording layer. Here, application by spin coating is shown as anexample. As the transfer layer UV cure resin 903, acrylic resin whichradically reacts with irradiation with UV rays is preferable as in thecase of Embodiment 1. Acrylic UV cure resin with a viscosity of 200MPa·s which can be easily peeled off the plastic (e.g., polycarbonate,olefin resin, etc.) (k−1)th stamper 902 is used. The transfer layerhaving a viscosity of 1 to 1000 MPa·s can well fit into projections anddepressions of guide grooves and pits on the stamper. Furthermore,through spinning at a speed of 4000 rpm for 5 seconds, a transfer layerof approximately 8 microns in thickness was obtained. Furthermore, theinside diameter of the coated transfer layer UV cure resin 903 is D2which is smaller than diameter D0 of the central hole of the (k−1)thstamper 902.

Then, as shown in FIG. 9( c), the (k−1)th stamper 902 coated with thetransfer layer UV cure resin 903 is superimposed on the kth signalsubstrate 900 on which the pressure-sensitive adhesive 901 issuperimposed in the chamber 908. At this time, suppose the degree ofvacuum in the chamber 908 is 1 to 100 hPa. Since D2<D1, thepressure-sensitive adhesive 901 will never contact the (k−1)th stamper902. After the formation of the (k−1)th separation layer, this isintended to prevent the pressure-sensitive adhesive 901 from directlycontacting the (k−1)th stamper 902 making it impossible to peel off the(k−1)th stamper 902 in the step of peeling the (k−1)th stamper 902.

Since the transfer layer UV cure resin 903 has a low viscosity, itspread when super imposed and a total average thickness of the transferlayer UV cure resin 903 and pressure-sensitive adhesive 901 became 30microns. After the superimposition, it is also possible to take out thekth signal substrate and the (k−1)th stamper into the atmosphere, crushbubbles produced when the kth signal substrate and the (k−1)th stamperare pressed against each other with a high-pressure compressed air orsecure the adhesion.

Finally as shown in FIG. 9( d), the uncured transfer layer UV cure resin903 is cured by UV rays using a UV lamp 910. As a result of the cure, a(k−1)th separation layer 909 which consists of the pressure-sensitiveadhesive 901 and transfer layer UV cure resin 903 is formed. Since UVrays penetrate to a certain degree if the (k−1)th stamper 902 istransparent, the transfer layer UV cure resin 903 can be well cured. Asthe UV lamp, a metal halide lamp, high pressure mercury lamp or xenonlamp, etc., can be used.

What is important in the steps shown in FIGS. 9( a)-9(d) is theselection of materials for the pressure-sensitive adhesive and transferUV cure resin. The pressure-sensitive adhesive needs to have strength ofadhesion to the kth signal recording layer and cured UV resin fortransfer layer. On the other hand, it goes without saying that it isimportant that the transfer UV cure resin be easily peeled from the(k−1)th stamper after the cure. After the steps shown in FIGS. 9(a)-9(d), it is possible to perform the peeling step shown in FIGS. 6(a)-6(d) as in the case of Embodiment 1.

In FIGS. 9( a)-9(d), the transfer layer UV cure resin 903 is applied tothe (k−1)th stamper 902, but it is also possible to apply the transferlayer UV cure resin 903 to the pressure-sensitive adhesive 901superimposed on the kth signal substrate 900. Furthermore, in FIG. 9,the pressure-sensitive adhesive 901 is superimposed on the kth signalsubstrate 900, but instead of this, it is also possible to apply thetransfer layer UV cure resin 903 to the (k−1)th stamper 902 and thensuperimpose the pressure-sensitive adhesive 901 on the (k−1)th stamper902 to which the transfer layer UV cure resin 903 is applied and thenpaste the kth signal substrate 900 to the (k−1)th stamper 902. It isalso possible to use the steps in FIG. 3( c), use the transfer UV cureresin 903 instead of the adhesive layer UV cure resin 307, rotate boththe (k−1)th stamper 902 and the kth signal substrate 900 to which thepressure-sensitive adhesive 901 is added to paste them together. Whenthe strength of adhesion between the pressure-sensitive adhesive 901 andtransfer layer UV cure resin 903 after the cure is insufficient, it isalso possible to arrange another adhesive capable of obtainingsufficient strength of adhesion to the transfer layer UV cure resin 903after the cure on the pressure-sensitive adhesive 901.

FIG. 10( a) shows a thickness distribution of the (k−1)th separationlayer 909 formed using the methods in FIGS. 8( a)-8(c)and FIGS. 9(a)-9(d). There is a distribution of about 1 micron of about 29.5 toabout 30.5 microns from the inside radius to the outside radius. This isdue to the thickness variation of the transfer layer UV cure resin 903by spin coating. This is more uniform than the (k−1)th separation layerof Embodiment 1 shown in FIG. 4( a). This is because apressure-sensitive adhesive with high thickness accuracy is used inEmbodiment 2.

FIG. 10( b) shows a case where the (k−1)th separation layer is formedusing the conventional flat (k−1)th stamper 500 as shown in FIGS. 5(a)-5(d) according to the method in FIGS. 9( a)-9(d). The distancebetween the kth signal substrate and the (k−1)th stamper is small at theinside radius and large at the outside radius, and therefore thethickness of the (k−1)th separation layer tends to increase from theinside radius to the outside radius and a distribution of about 6microns between about 27 and about 33 microns is produced. In this way,FIGS. 8( a)-8(c) and FIGS. 9( a)-(d) are effective for uniformity in thethickness of the (k−1)th separation layer.

In addition to the adhesion method of the pressure-sensitive adhesive tothe kth signal substrate in this Embodiment 2 ((FIG. 9( a)), a method ofpasting using a roller in the atmosphere or under a reduced pressure isalso available.

Furthermore, in Embodiment 2, it is also possible to create the (k−1)thseparation layer of a uniform thickness using the adhesive layer UV cureresin shown in Embodiment 1 according to the method shown in FIGS. 3(a)-3(d) instead of the pressure-sensitive adhesive. On the contrary,when the kth signal substrate is warped so as to wrap around the kthsignal recording layer as in the case of Embodiment 1, it is alsopossible to apply the pressure-sensitive adhesive shown in FIGS. 9(a)-9(d).

In above described Embodiment 2, the plastic (k−1)th stamper of 1.1 mmin thickness was used, but any plastic stamper that has a thickness ofat least about 0.5 mm is acceptable. If the stamper has a thickness ofabout 0.5 mm or more, since it also has rigidity, its shape can beeasily controlled according to the molding condition using the injectionmolding method and it can be easily handled, which is suited toimproving productivity.

Furthermore, Embodiment 2 has described the case where the (k−1)thseparation layer is made of two materials, but it is also applicable toa case where the (k−1)th separation layer is made of three or morematerials. Furthermore, Embodiment 2 has been described using UV cureresin, but it is also possible to use a radiation cure materialincluding a heat cure material.

Embodiment 3

Here, an alternative method for the method of manufacturing the (k−1)thstamper shown in FIGS. 2( a)-2(b) will be explained. FIGS. 12( a)-12(b)are schematic views of a molding metal die provided with a heatinsulator. This is intended to warp the (k−1)th stamper so as to wraparound the surface opposite to the surface on which guide grooves andpits are provided.

FIG. 12( a) shows a case where a heat insulator 1200 is provided betweena master stamper 201 and a metal die mirrored surface A. Cooling waterflows through a cooling water channel A and a cooling water channel B tocool melted polycarbonate 202 introduced inside a cavity 203 of amolding metal die 200. By inserting the heat insulator 1200, the metaldie mirrored surface B side is cooled according to the temperature ofthe cooling water that flows through the cooling water channel B, whilefor the master stamper 201 side, the temperature of the meltedpolycarbonate 202 is hardly cooled and therefore the master stamper 201is warped more than the (k−1)th stamper molded with the molding metaldie shown in FIGS. 2( a)-2(b). Cooling water can be flown through thecooling water channel A at a temperature necessary and enough to preventthe heat insulator 1200 from being broken by heat. FIG. 12( b) shows amolding metal die with a heat insulator 1203 incorporated behind themetal die mirrored surface A. With this configuration, it is alsopossible to achieve the same effect.

Moreover, in addition to FIGS. 12( a)-12(b), it is also possible toincorporate a heat insulator behind the metal die mirrored surface B. Inthis case, the temperature of the surface of the metal die mirroredsurface B tends to exceed the temperature on the master stamper side.For this reason, the molded (k−1)th stamper is warped so as to wraparound the surface opposite to the surface with guide grooves and pits.

Moreover, it is also possible to incorporate the heat insulator not onlyon one side of the metal die mirrored surface of the above describedpair of molding metal dies but also on both metal die mirrored surfaces.

In above described Embodiment 3, the plastic (k−1)th stamper of 1.1 mmin thickness is used, but any plastic stamper that has a thickness of atleast about 0.5 mm is acceptable. If the stamper has a thickness ofabout 0.5 mm or more, since it also has rigidity, its shape can beeasily controlled according to the molding condition using the injectionmolding method and it can be easily handled, which is suited toimproving productivity.

Embodiment 4

Embodiment 4 will describe the method of creating a metal (k−1)thstamper. Since metal has a relatively high degree of hardness, it ispossible to suppress damage or deformation which may occur to the(k−1)th stamper when the (k−1)th stamper is peeled off the kth signalsubstrate and is therefore effective. Projections and depressions ofguide grooves and pits must be switched round between the master stamper201 and the (k−1)th stamper also shown in FIGS. 2( a)-2(b) and FIGS. 12(a)-12(b). Therefore, it is possible to create a metal (k−1)th stamperusing the master stamper 201.

A master stamper is generally created using a glass master original diskhaving a shape whose projections and depressions are reverse to theguide grooves and pits on the master stamper. The surface of the glassmaster original disk is provided with projections and depressions whichare guide grooves and pits formed on its glass surface using aphotoresist. First, a photoresist is applied uniformly to the surface ofa glass plate and the photoresist is exposed to condensed laser with UVto far-ultraviolet wavelengths and further electronic rays into theshapes of guide grooves and pits. The exposed photoresist area isremoved in a developing step and projections and depressions such asguide grooves and pits are formed on the glass master original disk.

Then, a nickel thin film is formed on the surface of guide grooves andpits of the glass master original disk by means of vapor deposition orsputtering and nickel is deposited by electrocasting using the nickelthin film as an electrode. Generally, nickel is deposited to a thicknessof 0.3 mm and a nickel plate is created on the surface of the glassmaster original disk. When the nickel plate is peeled off the glassmaster original disk, a master stamper having projections anddepressions (guide grooves and pits) which are reversed projections anddepressions (guide grooves and pits) on the glass master original diskis formed on the nickel plate.

The method of creating a nickel (k−1)th stamper from the nickel masterstamper will be shown below.

(1) Surface Oxidation Treatment of Surface with Projections andDepressions (Guide Grooves and Pits) of Master Stamper

The master stamper is immersed in an aqueous solution of sodiumhydroxide and used as an anode with a current of 20 A flowing for 60seconds. In this way, an oxide film with the surface with projectionsand depressions of the master stamper subjected to oxidation treatmentis formed.

(2) Formation of Nickel (k−1)th Stamper on Surface with Projections andDepressions of Master Stamper through Electrocasting

The entire master stamper is immersed in an electrocasting bath and thisis used as a negative electrode to perform electrocasting. Anelectrocasting bath of nickel sulfamate (concentration: 550 g/L) andboric acid (concentration: 31 g/L) is used. The pH value, temperatureand current density during electrocasting of the electrocasting bath areadjusted as required. Nickel is formed to a thickness of about 0.3 mm ona master stamper by electrocasting and about 0.3 mm nickel (k−1)thstamper is obtained.

(3) Peeling and Punching of Nickel (k−1)th Stamper

The nickel (k−1)th stamper is peeled off the master stamper and punchedout to a necessary outside radius and inside radius.

The method of creating the (k−1)th stamper has been presented briefly sofar. To control the warpage of the metal (k−1)th stamper according tothe shape of the kth signal substrate, the pH value, temperature andcurrent density during electrocasting of the electrocasting bath in (2)above can be controlled. FIGS. 13( a)-13(c) show variations of warpageof the (k−1)th stamper corresponding to parameters when the (k−1)thstamper is created by changing the current density, temperature of theelectrocasting bath and pH value during electrocasting. Here, + in thewarpage direction means that the (k−1)th stamper is warped opposite tothe surface with projections and depressions of the (k−1)th stamper,whereas − in the warpage direction means that the (k−1)th stamper iswarped according to the surface with projections and depressions of the(k−1)th stamper. The magnitude of warpage is indicated with an angleformed by a tangential line of the (k−1)th stamper with respect to theradial direction of the (k−1)th stamper.

As shown in FIG. 13( a), the current density changes between + warpageand − warpage with 20 amperes/dm^2 as the border. In FIG. 13( b),warpage is + when the temperature of the electrocasting bath is lowerthan about 45° C., whereas warpage is − when the temperature of theelectrocasting bath is higher than about 45° C. In the case of pH of theelectrocasting bath in FIG. 13( c), warpage reaches a minimum with aboutpH 4.5, that is, the (k−1)th stamper becomes fiat and warpage is + as itgoes away from the minimum value. As shown above, when the (k−1)thstamper is created through electrocasting, if electrocasting isperformed by controlling at least one of current density duringelectrocasting, temperature of the electrocasting bath and pH value, itis possible to control warpage of the (k−1)th stamper. With theseparameters, it is possible to create the (k−1)th stamper in a shapeparallel to the kth signal substrate.

For the metal (k−1)th stamper created in the above steps, it is possibleto form a separation layer in a space with the kth signal substrateusing the method shown in FIGS. 3( a)-3(d) and FIGS. 9( a)-9(d).However, when the separation layer is formed, the metal (k−1)th stamperis opaque and has no UV permeability, and therefore it is necessary touse radiation rays such as far-infrared rays for curing using aradiation-cured material such as a heat cure material instead of theadhesive layer UV cure resin 307 or transfer layer UV cure resin 903.Furthermore, a pressure-sensitive adhesive can also be used instead ofthe adhesive layer UV cure resin 307. After the separation layer isformed, peeling off the kth signal substrate is possible using themethod shown in FIG. 6.

Furthermore, nickel is used as metal in Embodiment 4, but any othermetal can be used as the material if it allows at least electrocasting.

Embodiment 5

An apparatus of manufacturing a multilayer optical information recordingmedium will be explained as Embodiment 5. The manufacturing apparatuscomprises shape maintaining means of arranging the kth signal substrateand the (k−1)th stamper in such a way that the kth signal recordinglayer and the surface with guide grooves and pits of the (k−1)th signalrecording layer facing each other and maintaining the shape so that the(k−1)th stamper and the kth signal substrate are shaped parallel to eachother, separation layer forming means of, when at least one of the(k−1)th stamper and the kth signal substrate is maintained by the shapemaintaining means in a shape parallel to each other, forming the (k−1)thseparation layer between the kth signal recording layer and the guidegrooves and pits of the (k−1)th signal recording layer and peeling meansof peeling the (k−1)th stamper from the interface between the (k−1)thseparation layer and the (k−1)th stamper. FIG. 14 and FIG. 15 showexamples of the shape maintaining means and the separation layer formingmeans.

The separation layer forming means of this embodiment is an example ofthe signal recording layer forming means of the present invention.

FIGS. 14( a)-14(d) are examples of cases where the shape maintainingmeans is an arm. A flat (k−1)th stamper 500 is used with a transferlayer 503 formed on the guide grooves and pits shown in FIG. 14( a). Thetransfer layer is formed using the method shown in FIGS. 5( a) and 5(b).A kth signal substrate 306 is warped so as to wrap around the kth signalrecording layer. Warpage measuring means 1401 calculates an angle ofinclination of the kth signal recording layer on the kth signalsubstrate by causing measuring light 1402 to enter the kth signalrecording layer on the kth signal substrate 306 and detecting theposition of the reflected measuring light 1402.

As shown in FIG. 14( b), the shape maintaining arm 1400 maintains thesurface opposite to the surface on which the transfer layer 503 of the(k−1)th stamper 500 is formed to the inside radius side and the outsideradius side. At this time, the shape maintaining arm 1400 maintains the(k−1)th stamper 500 in a warped position so that guide grooves and pitsof the (k−1)th signal recording layer are kept parallel to the kthsignal recording layer according to the angle of inclination of the kthsignal recording layer obtained from the warpage measuring means 1401.That is, the warpage measuring means 1401 measures the surface shape ofthe kth signal recording layer of one or a plurality of the kth signalsubstrates 306 manufactured currently or in the past and the shapemaintaining arm 1400 shapes the surface with the guide grooves and/orpits of the (k−1)th signal recording layer of the (k−1)th stamper 500 insuch a way as to conform to the surface shape of the kth signalsubstrate 306 based on the measurement result. That is, the shapemaintaining arm 1400 forms the (k−1)th stamper 500 in a shape parallelto the shape of the kth signal substrate 306 based on the measurementresult.

Then, the shape of the kth signal substrate 306 may be measured bymeasuring the shape of the kth signal substrate 306 manufactured firstin the morning the day before when the plant operates and determiningthe shape of the (k−1)th stamper 500 based on the measurement result.Furthermore, it is also possible to measure the shape of the kth signalsubstrates 306 one by one every time the kth signal substrate 306 ismanufactured and determine the shape of the (k−1)th stamper 500 based onthe measurement result. Furthermore, it is also possible to determinethe shape of the (k−1)th stamper 500 using the measurement result of theshape of the kth signal substrate 306 for each lot.

In order to change the shape of the (k−1)th stamper 500, the memberwhich holds the stamper of the shape maintaining arm 1400 has drivingmeans such as an air cylinder, stepping motor and actuator, etc.Furthermore, the holding method includes vacuum suction and a mechanicalholding method such as a lug in the case of the outside radius side.

Then, as shown in FIG. 14( c), with the shape of the (k−1)th stamper 500maintained, adhesive layer UV cure resin 307 which becomes part of the(k−1)th separation layer is applied in the space with the kth signalsubstrate 306. The nozzle 1403 is inserted between the (k−1)th stamper500 and the kth signal substrate 306 and adhesive layer UV cure resin307 is dribbled in the inside radius area of the kth signal substrate306. At this time, the kth signal substrate 306 is held on the table 309and the adhesive layer UV cure resin 307 is dribbled like a ring whenthe table 309 is turned. Since the (k−1)th stamper 500 is held by theshape maintaining arm 1400, the distance from the kth signal substrate306 can be kept uniform in the radial direction.

Then, while the shape of the (k−1)th stamper 500 is maintained by theshape maintaining arm 1400, the table 309 which holds the kth signalsubstrate 306 is turned. At this time, the shape maintaining arm 1400also rotates in synchronization with the table 309 while holding the(k−1)th stamper 500. Through this rotation, the adhesive layer UV cureresin 307 spreads in the radial direction and forms a uniform adhesivelayer between the (k−1)th stamper 500 and the kth signal substrate 306.With the shape of the (k−1)th stamper 500 maintained by the shapemaintaining arm 1400, the adhesive layer is cured by UV rays and peelingis performed as shown in FIGS. 6( a)-6(d). The lug 610 in FIGS. 6(a)-6(d) and the handling means 612 constitute part of the peeling means.

Furthermore, when the kth signal substrate is warped so as to wraparound the surface opposite to the surface on which the kth signalrecording layer is placed, the shape maintaining arm 1400 holds the(k−1)th stamper 500 as shown in FIG. 14( d).

FIGS. 15( a)-15(d) show cases where the shape maintaining means has atable shape. A flat (k−1)th stamper 500 with a transfer layer 503 formedon guide grooves and pits shown in FIG. 15( a) is used. The transferlayer is formed using the method shown in FIGS. 5( a) and 5(b). The kthsignal substrate 306 is warped so as to wrap around the kth signalrecording layer. The warpage measuring means 1401 calculates an angle ofinclination of the kth signal recording layer on the kth signalsubstrate by causing measuring light 1402 to enter the kth signalrecording layer on the kth signal substrate 306 and detecting theposition of the reflected measuring light 1402.

As shown in FIG. 15( b), the shape maintaining table 1500 holds thesurface of the (k−1)th stamper 500 on which the transfer layer 503 isformed. At this time, the shape maintaining table 1500 holds the (k−1)thstamper 500 warped so that guide grooves and pits of the (k−1)th signalrecording layer are kept parallel to the kth signal recording layeraccording to the angle of inclination of the kth signal recording layerobtained from the warpage measuring means 1401. That is, according tothe angle of inclination of the kth signal recording layer, either aconvex shape maintaining table 1500 which shapes the (k−1)th stamper 500so as to wrap around the surface opposite to the surface provided withguide grooves and pits as shown in FIG. 15( b) or a concave shapemaintaining table 1501 which shapes the (k−1)th stamper 500 so as towrap around the surface provided with guide grooves and pits as shown inFIG. 15( d) is selected and the (k−1)th stamper 500 is held.Furthermore, the holding method includes vacuum suction and a mechanicalholding method such as a lug in the case of the outside radius side.

Then, as shown in FIG. 15( c), with the shape of the (k−1)th stamper 500maintained, adhesive layer UV cure resin 307 which becomes part of the(k−1)th separation layer is applied in the space with the kth signalsubstrate 306. The nozzle 1403 is inserted between the (k−1)th stamper500 and the kth signal substrate 306 and adhesive layer UV cure resin307 is dribbled in the inside radius area of the kth signal substrate306. At this time, the kth signal substrate 306 is held on the table 309and the adhesive layer UV cure resin 307 is dribbled like a ring whenthe table 309 is turned. Since the (k−1)th stamper 500 is held by theshape maintaining table 1500, the distance from the kth signal substrate306 can be kept uniform in the radial direction.

Then, while the shape of the (k−1)th stamper 500 is maintained by theshape maintaining table 1500, the table is turned. Through thisrotation, the adhesive layer UV cure resin 307 spreads in the radialdirection and forms a uniform adhesive layer between the (k−1)th stamper500 and the kth signal substrate 306. With the shape of the (k−1)thstamper maintained by the shape maintaining table 1500, the adhesivelayer is cured by UV rays and peeling is performed as shown in FIGS. 6(a)-6(d). The lug 610 in FIGS. 6( a)-6(d) and the handling means 612constitute part of the peeling means.

FIG. 15( c) has shown the method of inserting the nozzle 1403 betweenthe kth signal substrate 306 and the (k−1)th stamper 500 and dribblingthe adhesive layer UV cure resin 307, but it is also possible to dribblethe adhesive layer UV cure resin 307 directly onto the (k−1)th stamperusing the nozzle and then drop the kth signal substrate on top of it.These two types of dribbling method can also be used in the steps inFIG. 3( c).

Embodiment 5 has described the method of forming the (k−1)th separationlayer from two types of material of the adhesive layer using thetransfer layer and UV cure resin, but Embodiment 5 is also applicablewhen the (k−1)th separation layer other than the transfer layer existson the kth signal substrate. For example, this embodiment is applicableto a method of dribbling a material which becomes a transfer layer on apressure-sensitive adhesive which exists on the kth signal substrate.

Furthermore, Embodiment 5 has described the method of changing the shapeof the (k−1)th stamper by the shape maintaining means according to theshape (warpage) of the kth signal substrate having a plurality of signalrecording layers, but it is also possible to change the shape of kthsignal substrate. Changing the shape generally distorts a plurality ofsignal recording layers, and therefore it is preferable to change theshape of the (k−1)th stamper.

Embodiment 5 has used the plastic (k−1)th stamper of 1.1 mm inthickness, but any plastic stamper that has a thickness of at leastabout 0.5 mm is acceptable. If the stamper has a thickness of about 0.5mm or more, since it also has rigidity, its shape can be easilycontrolled according to the molding condition using the injectionmolding method and it can be easily handled, which is suited toimproving productivity. Furthermore, the metal stamper shown inEmbodiment 4 can also be used instead of the plastic (k−1)th stamper.

Furthermore, Embodiment 5 has described the case where the plastic(k−1)th separation layer is made of two materials, but this embodimentis also applicable to a case where the (k−1)th separation layer is madeof three or more materials. Furthermore, Embodiment 5 has been describedusing UV cure resin, but it is also possible to use a radiation cure,material including a heat cure material.

As described above, the method of manufacturing the multilayer opticalinformation recording medium of the present invention forms the (k−1)thseparation layer by maintaining the kth signal recording layer of thekth signal substrate and the surface provided with guide grooves or pitsor guide grooves and pits of the (k−1)th stamper in a shape parallel toeach other, and can thereby keep constant the distance between the kthsignal recording layer of the kth signal substrate and the surfaceprovided with guide grooves or pits or guide grooves and pits of the(k−1)th stamper and keep uniform the thickness of the (k−1)th separationlayer formed.

1. A method of manufacturing a multilayer optical information recordingmedium comprising: providing a substrate having a central hole and asurface, wherein the substrate comprises at least one signal recordinglayer(s) and wherein one of the at least one signal recording layer(s)is provided on the surface of the substrate, fixing said substrate to asupport base having a central hole configured to allow air to flowtherethrough, measuring a surface shape of one or a plurality of saidsubstrates, shaping a stamper such that the stamper is provided with (1)guide grooves and/or pits corresponding to an additional signalrecording layer, (2) a central hole, and (3) a shape which correspondsto said measured surface, forming a separation layer having a centralhole by providing a material between the stamper and the substrate suchthat the separation layer separates the signal recording layer providedon the surface of the substrate from the additional signal recordinglayer provided on the stamper, attaching a handling means to thestamper, and peeling the stamper from the separation layer by (1)inserting a lug into the central holes of the separation layer and thestamper, (2) introducing pressurized air from the central hole of thesupport base while opening the lug outward, and (3) pulling up thehandling means.
 2. The method of manufacturing the multilayer opticalinformation recording medium according to claim 1, wherein: the one ofthe at least one recording layer(s) provided on the surface of thesubstrate faces away From the support base, and a surface of the stamperprovided with the guide grooves and/or pits faces the support base. 3.The method of manufacturing the multilayer optical information recordingmedium according to claim 2, wherein: said one of said substrates iswarped away from the support base, and said stamper is warped away fromthe support base.
 4. The method of manufacturing the multilayer opticalinformation recording medium according to claim 2, wherein: said one ofsaid substrates is warped toward the support base, and said stamper iswarped toward the support base.
 5. The method of manufacturing themultilayer optical information recording medium according to claim 3 or4, wherein in said forming step, the one of the at least one signalrecording layers provided on the surface of the substrate and thesurface of the stamper provided with the guide grooves and/or pits areshaped so as to have substantially the same radius of curvature.
 6. Themethod of manufacturing the multilayer optical information recordingmedium according to claim 1, wherein said separation layer is radiationcure resin.
 7. The method of manufacturing the multilayer opticalinformation recording medium according to claim 6, wherein saidradiation cure resin is UV cure resin.
 8. The method of manufacturingthe multilayer optical information recording medium according to claim1, wherein said separation layer consists of a plurality of layers. 9.The method of manufacturing the multilayer optical information recordingmedium according to claim 8, wherein: one of the plurality of layers ofsaid separation layer, which contacts the surface of the stamperprovided with the guide grooves and/or pits, is a transfer layer, and aninterface between said transfer layer and said stamper is an interfacewhich is most easily peeled off.
 10. The method of manufacturing themultilayer optical information recording medium according to claim 9,wherein at least said transfer layer is a radiation cure material. 11.The method of manufacturing the multilayer optical information recordingmedium according to claim 10, wherein said radiation cure material is UVcure resin.
 12. The method of manufacturing the multilayer opticalinformation recording medium according to claim 11, wherein theviscosity of said UV cure resin is about 1 to 1000 mPa·s.
 13. The methodof manufacturing the multilayer optical information recording mediumaccording to claim 8, wherein: one of the plurality of layers of saidseparation layer, which contacts the surface of the stamper providedwith the guide grooves and/or pits, is a transfer layer, and at leastone of said plurality of layers of said separation layer other than thetransfer layer is a pressure-sensitive adhesive.
 14. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 13, wherein said pressure-sensitive adhesive issuperimposed gradually starting from a central area outward in a chambervacuum-sealed in the degree of 1 to 100 hPa and then pressed by ahigh-pressure compressed air to secure the adhesion.
 15. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 8, wherein the forming step further includes: coatingthe surface of the stamper provided with the guide grooves and/or pitswith a radiation cure material which becomes a transfer layer of theplurality of layers of the separation layer; curing the radiation curematerial; forming at least one other layer of the plurality of layers ofthe separation layer on the one of the at least one signal recordinglayer(s) provided on the surface of the substrate; and attaching thetransfer layer to the at least one other layer of the plurality oflayers of the separation layer.
 16. The method of manufacturing themultilayer optical information recording medium according to claim 15,wherein the at least one other layer of the plurality of layers of theseparation layer is a radiation cure material.
 17. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 8, wherein the forming step further includes: formingat least one of the plurality of layers of the separation layer on theone of the at least one signal recording layer(s) provided on thesurface of the substrate; disposing a radiation cure material betweensaid stamper and the at least one of the plurality of layers of theseparation layer; and curing the radiation cure material to form atransfer layer of the plurality of layers of the separation layer. 18.The method of manufacturing the multilayer optical information recordingmedium according to claim 17, wherein the disposing step furtherincludes applying the radiation cure material to the at least one of theplurality of layers of the separation layer cure.
 19. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 15, wherein said stamper is held in such a way thatsaid stamper is shaped parallel to said one of the at least one signalrecording layer(s) and then said radiation cure material is cured. 20.The method of manufacturing the multilayer optical information recordingmedium according to claim 2, wherein said stamper is made of plastic.21. The method of manufacturing the multilayer optical informationrecording medium according to claim 20, wherein said plastic istransparent.
 22. The method of manufacturing the multilayer opticalinformation recording medium according to claim 21, wherein said stamperis any one of polycarbonate, olefin resin, acrylic resin ornorbornen-based resin.
 23. The method of manufacturing the multilayeroptical information recording medium according to claim 22, wherein saidstamper is formed by injection molding so as to be shaped parallel tosaid substrate.
 24. The method of manufacturing the multilayer opticalinformation recording medium according to claim 23, wherein the shapingstep further includes; disposing a master stamper on a first metal diemirrored surface; disposing a polycarbonate material between the firstmetal die mirrored surface and a second metal die mirrored surface,setting a temperature of the second metal die mirrored surface higherthan a temperature of the master stamper, thereby to form a warpedstamper which, when placed so that the surface of the stamper providedwith the guide grooves and/or pits faces the table, warps away from thetable.
 25. The method of manufacturing the multilayer opticalinformation recording medium according to claim 24, wherein the shapingstep further comprises setting the temperature of the second metal diemirrored surface higher than a temperature of the first metal diemirrored surface.
 26. The method of manufacturing the multilayer opticalinformation recording medium according to claim 24, wherein coolingwater channels are provided with both of upper and lower sides of thefirst metal die mirrored surface, and a heat insulator is placed on aback surface of the second metal die mirrored surface.
 27. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 23, wherein the shaping step further includes:disposing a master stamper on a first metal die mirrored surface;disposing a polycarbonate material between the first metal die mirroredsurface and a second metal die mirrored surface; and setting atemperature of the master stamper higher than a temperature of thesecond metal die mirrored surface, thereby to form a warped stamperwhich, when placed so that the surface of the stamper provided with theguide grooves and/or pits faces the table, warps toward the table. 28.The method of manufacturing the multilayer optical information recordingmedium according to claim 27, wherein the shaping step further comprisessetting a temperature of the first metal die mirrored surface higherthan the temperature of the second metal die mirrored surface.
 29. Themethod of manufacturing the multilayer optical information recordingmedium according to claim 27, wherein a heat insulator is placed on atleast one of a back surface of said metal master stamper and a backsurface of the first metal die mirrored surface.
 30. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 1, wherein said stamper is metal.
 31. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 30, wherein in said shaping step: said stamper iscreated by electrocasting; said substrate and said stamper are arrangedwith said one of said at least one signal recording layers and thesurface of the stamper provided with the guide grooves and/or pitsfacing each other under at least one electrocasting condition of a pHvalue, a temperature and a current density of an electrocasting bathduring electrocasting, said stamper is controlled so as to be shapedparallel to said substrate.
 32. The method of manufacturing themultilayer optical information recording medium according to claim 1,further comprising a film forming step after said peeling step, ofcompleting an additional one of the at least one signal recordinglayer(s) by forming one of a recording multilayer film or a reflectingfilm on the guide grooves and/or pits of said additional signalrecording layer.
 33. The method of manufacturing the multilayer opticalinformation recording medium according to claim 1, wherein: the formingstep further comprises forming a recording multilayer film or areflecting film on the surface of the stamper provided with the guidegrooves and/or pits, and said peeling step, further comprises peelingoff said stamper from an interface formed between said recordingmultilayer film and said stamper, wherein said recording multilayer filmor said reflecting film is moved onto said separation layer.
 34. Themethod of manufacturing the multilayer optical information recordingmedium according to claim 1, wherein a transparent cover layer is formedon the one of the at least one signal recording layer(s).
 35. The methodof manufacturing the multilayer optical information recording mediumaccording to claim 34, wherein said transparent cover layer is formed byadhering a transparent substrate to the one of the at least one signalrecording layer(s) with a transparent adhesive.
 36. The method ofmanufacturing the multilayer optical information recording mediumaccording to claim 34, wherein said transparent cover layer is formed ofa transparent radiation cure material.
 37. The method of manufacturingthe multilayer optical information recording medium according to claim34, wherein at least part of said transparent cover layer is formed of apressure-sensitive adhesive.
 38. The method of manufacturing themultilayer optical information recording medium according to claim 34,wherein the thickness of the transparent cover layer is 0.3 mm or less.39. An apparatus for manufacturing a multilayer optical informationrecording medium having a central hole comprising: a support basecomprising a central hole for fixing a substrate having a central holesuch that the central holes of the support base and the substrate aresuperimposed, wherein the substrate comprises at least one signalrecording layer(s) and wherein one of the at least signal recordinglayer(s) is provided on a surface of the substrate, measuring means formeasuring a surface shape of one or a plurality of the substrates, ashaping means for providing the stamper with (1) guide grooves and/orpits corresponding to an additional signal recording layer, (2) acentral hole, and (3) a shape which corresponds to said measuredsurface, forming means for producing a separation layer having a centralhole by providing a material between the stamper and the substrate suchthat the separation layer separates the signal recording layer providedon the surface of the substrate from the additional signal recodinglayer provided on the stamper, and peeling means comprising (1) a lugwhich is inserted into the central holes of the separation layer and thestamper, wherein the lug can be opened outwardly, (2) a source orpressurized air which delivers pressurized air to the central hole ofthe support base while the lug is opened outwardly, and (3) a handlingmeans which attaches to the stamper such that it may be pulled up topeel the stamper from the separation layer.
 40. The apparatus ofmanufacturing the multilayer optical information recording mediumaccording to claim 39, wherein the shaping means comprises a mechanismwhich holds the stamper so that when the substrate is warped, the guidegrooves and/or pits of the additional signal recording layer and the oneof the at least one signal recording layer are parallel to each otheraccording to the warpage of the substrate.
 41. The apparatus ofmanufacturing the multilayer optical information recording mediumaccording to claim 40, wherein the shaping means has a shape of around-table and has a surface shape that contacts the stamper so thatthe guide grooves and/or pits of the additional signal recording layerare parallel to the one of the at least one signal recording layer. 42.The apparatus of manufacturing the multilayer optical informationrecording medium according to claim 39, wherein the shaping meanssupports the surface of at least one of the stamper and the signalsubstrate for which the additional separation layer is not formed by“vacuum suction”.